android_kernel_xiaomi_sm8350/drivers/net/wireless/Kconfig
Adrian Bunk 94d9842403 remove the strip driver
The latest trace about usage of this driver I found was an (unanswered)
request for help by a user trying to get it working reliably five years
ago with kernel 2.4 .

And even if it was still working the use cases of this driver (requiring
both the hardware and someone providing this kind of wireless network)
have become practically nonexisting.

This patch therefore removes the strip driver.

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
2008-06-26 16:49:13 -04:00

675 lines
23 KiB
Plaintext

#
# Wireless LAN device configuration
#
menu "Wireless LAN"
depends on !S390
config WLAN_PRE80211
bool "Wireless LAN (pre-802.11)"
depends on NETDEVICES
---help---
Say Y if you have any pre-802.11 wireless LAN hardware.
This option does not affect the kernel build, it only
lets you choose drivers.
config ARLAN
tristate "Aironet Arlan 655 & IC2200 DS support"
depends on ISA && !64BIT && WLAN_PRE80211
select WIRELESS_EXT
---help---
Aironet makes Arlan, a class of wireless LAN adapters. These use the
www.Telxon.com chip, which is also used on several similar cards.
This driver is tested on the 655 and IC2200 series cards. Look at
<http://www.ylenurme.ee/~elmer/655/> for the latest information.
The driver is built as two modules, arlan and arlan-proc. The latter
is the /proc interface and is not needed most of time.
On some computers the card ends up in non-valid state after some
time. Use a ping-reset script to clear it.
config WAVELAN
tristate "AT&T/Lucent old WaveLAN & DEC RoamAbout DS ISA support"
depends on ISA && WLAN_PRE80211
select WIRELESS_EXT
---help---
The Lucent WaveLAN (formerly NCR and AT&T; or DEC RoamAbout DS) is
a Radio LAN (wireless Ethernet-like Local Area Network) using the
radio frequencies 900 MHz and 2.4 GHz.
If you want to use an ISA WaveLAN card under Linux, say Y and read
the Ethernet-HOWTO, available from
<http://www.tldp.org/docs.html#howto>. Some more specific
information is contained in
<file:Documentation/networking/wavelan.txt> and in the source code
<file:drivers/net/wireless/wavelan.p.h>.
You will also need the wireless tools package available from
<http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Tools.html>.
Please read the man pages contained therein.
To compile this driver as a module, choose M here: the module will be
called wavelan.
config PCMCIA_WAVELAN
tristate "AT&T/Lucent old WaveLAN Pcmcia wireless support"
depends on PCMCIA && WLAN_PRE80211
select WIRELESS_EXT
help
Say Y here if you intend to attach an AT&T/Lucent Wavelan PCMCIA
(PC-card) wireless Ethernet networking card to your computer. This
driver is for the non-IEEE-802.11 Wavelan cards.
To compile this driver as a module, choose M here: the module will be
called wavelan_cs. If unsure, say N.
config PCMCIA_NETWAVE
tristate "Xircom Netwave AirSurfer Pcmcia wireless support"
depends on PCMCIA && WLAN_PRE80211
select WIRELESS_EXT
help
Say Y here if you intend to attach this type of PCMCIA (PC-card)
wireless Ethernet networking card to your computer.
To compile this driver as a module, choose M here: the module will be
called netwave_cs. If unsure, say N.
config WLAN_80211
bool "Wireless LAN (IEEE 802.11)"
depends on NETDEVICES
---help---
Say Y if you have any 802.11 wireless LAN hardware.
This option does not affect the kernel build, it only
lets you choose drivers.
config PCMCIA_RAYCS
tristate "Aviator/Raytheon 2.4MHz wireless support"
depends on PCMCIA && WLAN_80211
select WIRELESS_EXT
---help---
Say Y here if you intend to attach an Aviator/Raytheon PCMCIA
(PC-card) wireless Ethernet networking card to your computer.
Please read the file <file:Documentation/networking/ray_cs.txt> for
details.
To compile this driver as a module, choose M here: the module will be
called ray_cs. If unsure, say N.
config IPW2100
tristate "Intel PRO/Wireless 2100 Network Connection"
depends on PCI && WLAN_80211
select WIRELESS_EXT
select FW_LOADER
select IEEE80211
---help---
A driver for the Intel PRO/Wireless 2100 Network
Connection 802.11b wireless network adapter.
See <file:Documentation/networking/README.ipw2100> for information on
the capabilities currently enabled in this driver and for tips
for debugging issues and problems.
In order to use this driver, you will need a firmware image for it.
You can obtain the firmware from
<http://ipw2100.sf.net/>. Once you have the firmware image, you
will need to place it in /lib/firmware.
You will also very likely need the Wireless Tools in order to
configure your card:
<http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Tools.html>.
It is recommended that you compile this driver as a module (M)
rather than built-in (Y). This driver requires firmware at device
initialization time, and when built-in this typically happens
before the filesystem is accessible (hence firmware will be
unavailable and initialization will fail). If you do choose to build
this driver into your kernel image, you can avoid this problem by
including the firmware and a firmware loader in an initramfs.
config IPW2100_MONITOR
bool "Enable promiscuous mode"
depends on IPW2100
---help---
Enables promiscuous/monitor mode support for the ipw2100 driver.
With this feature compiled into the driver, you can switch to
promiscuous mode via the Wireless Tool's Monitor mode. While in this
mode, no packets can be sent.
config IPW2100_DEBUG
bool "Enable full debugging output in IPW2100 module."
depends on IPW2100
---help---
This option will enable debug tracing output for the IPW2100.
This will result in the kernel module being ~60k larger. You can
control which debug output is sent to the kernel log by setting the
value in
/sys/bus/pci/drivers/ipw2100/debug_level
This entry will only exist if this option is enabled.
If you are not trying to debug or develop the IPW2100 driver, you
most likely want to say N here.
config IPW2200
tristate "Intel PRO/Wireless 2200BG and 2915ABG Network Connection"
depends on PCI && WLAN_80211
select WIRELESS_EXT
select FW_LOADER
select IEEE80211
---help---
A driver for the Intel PRO/Wireless 2200BG and 2915ABG Network
Connection adapters.
See <file:Documentation/networking/README.ipw2200> for
information on the capabilities currently enabled in this
driver and for tips for debugging issues and problems.
In order to use this driver, you will need a firmware image for it.
You can obtain the firmware from
<http://ipw2200.sf.net/>. See the above referenced README.ipw2200
for information on where to install the firmware images.
You will also very likely need the Wireless Tools in order to
configure your card:
<http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Tools.html>.
It is recommended that you compile this driver as a module (M)
rather than built-in (Y). This driver requires firmware at device
initialization time, and when built-in this typically happens
before the filesystem is accessible (hence firmware will be
unavailable and initialization will fail). If you do choose to build
this driver into your kernel image, you can avoid this problem by
including the firmware and a firmware loader in an initramfs.
config IPW2200_MONITOR
bool "Enable promiscuous mode"
depends on IPW2200
---help---
Enables promiscuous/monitor mode support for the ipw2200 driver.
With this feature compiled into the driver, you can switch to
promiscuous mode via the Wireless Tool's Monitor mode. While in this
mode, no packets can be sent.
config IPW2200_RADIOTAP
bool "Enable radiotap format 802.11 raw packet support"
depends on IPW2200_MONITOR
config IPW2200_PROMISCUOUS
bool "Enable creation of a RF radiotap promiscuous interface"
depends on IPW2200_MONITOR
select IPW2200_RADIOTAP
---help---
Enables the creation of a second interface prefixed 'rtap'.
This second interface will provide every received in radiotap
format.
This is useful for performing wireless network analysis while
maintaining an active association.
Example usage:
% modprobe ipw2200 rtap_iface=1
% ifconfig rtap0 up
% tethereal -i rtap0
If you do not specify 'rtap_iface=1' as a module parameter then
the rtap interface will not be created and you will need to turn
it on via sysfs:
% echo 1 > /sys/bus/pci/drivers/ipw2200/*/rtap_iface
config IPW2200_QOS
bool "Enable QoS support"
depends on IPW2200 && EXPERIMENTAL
config IPW2200_DEBUG
bool "Enable full debugging output in IPW2200 module."
depends on IPW2200
---help---
This option will enable low level debug tracing output for IPW2200.
Note, normal debug code is already compiled in. This low level
debug option enables debug on hot paths (e.g Tx, Rx, ISR) and
will result in the kernel module being ~70 larger. Most users
will typically not need this high verbosity debug information.
If you are not sure, say N here.
config LIBERTAS
tristate "Marvell 8xxx Libertas WLAN driver support"
depends on WLAN_80211
select WIRELESS_EXT
select FW_LOADER
---help---
A library for Marvell Libertas 8xxx devices.
config LIBERTAS_USB
tristate "Marvell Libertas 8388 USB 802.11b/g cards"
depends on LIBERTAS && USB
---help---
A driver for Marvell Libertas 8388 USB devices.
config LIBERTAS_CS
tristate "Marvell Libertas 8385 CompactFlash 802.11b/g cards"
depends on LIBERTAS && PCMCIA
select FW_LOADER
---help---
A driver for Marvell Libertas 8385 CompactFlash devices.
config LIBERTAS_SDIO
tristate "Marvell Libertas 8385 and 8686 SDIO 802.11b/g cards"
depends on LIBERTAS && MMC
---help---
A driver for Marvell Libertas 8385 and 8686 SDIO devices.
config LIBERTAS_DEBUG
bool "Enable full debugging output in the Libertas module."
depends on LIBERTAS
---help---
Debugging support.
config AIRO
tristate "Cisco/Aironet 34X/35X/4500/4800 ISA and PCI cards"
depends on ISA_DMA_API && WLAN_80211 && (PCI || BROKEN)
select WIRELESS_EXT
select CRYPTO
---help---
This is the standard Linux driver to support Cisco/Aironet ISA and
PCI 802.11 wireless cards.
It supports the new 802.11b cards from Cisco (Cisco 34X, Cisco 35X
- with or without encryption) as well as card before the Cisco
acquisition (Aironet 4500, Aironet 4800, Aironet 4800B).
This driver support both the standard Linux Wireless Extensions
and Cisco proprietary API, so both the Linux Wireless Tools and the
Cisco Linux utilities can be used to configure the card.
The driver can be compiled as a module and will be named "airo".
config HERMES
tristate "Hermes chipset 802.11b support (Orinoco/Prism2/Symbol)"
depends on (PPC_PMAC || PCI || PCMCIA) && WLAN_80211
select WIRELESS_EXT
---help---
A driver for 802.11b wireless cards based on the "Hermes" or
Intersil HFA384x (Prism 2) MAC controller. This includes the vast
majority of the PCMCIA 802.11b cards (which are nearly all rebadges)
- except for the Cisco/Aironet cards. Cards supported include the
Apple Airport (not a PCMCIA card), WavelanIEEE/Orinoco,
Cabletron/EnteraSys Roamabout, ELSA AirLancer, MELCO Buffalo, Avaya,
IBM High Rate Wireless, Farralon Syyline, Samsung MagicLAN, Netgear
MA401, LinkSys WPC-11, D-Link DWL-650, 3Com AirConnect, Intel
IPW2011, and Symbol Spectrum24 High Rate amongst others.
This option includes the guts of the driver, but in order to
actually use a card you will also need to enable support for PCMCIA
Hermes cards, PLX9052 based PCI adaptors or the Apple Airport below.
You will also very likely also need the Wireless Tools in order to
configure your card and that /etc/pcmcia/wireless.opts works :
<http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Tools.html>
config APPLE_AIRPORT
tristate "Apple Airport support (built-in)"
depends on PPC_PMAC && HERMES
help
Say Y here to support the Airport 802.11b wireless Ethernet hardware
built into the Macintosh iBook and other recent PowerPC-based
Macintosh machines. This is essentially a Lucent Orinoco card with
a non-standard interface.
This driver does not support the Airport Extreme (802.11b/g). Use
the BCM43xx driver for Airport Extreme cards.
config PLX_HERMES
tristate "Hermes in PLX9052 based PCI adaptor support (Netgear MA301 etc.)"
depends on PCI && HERMES
help
Enable support for PCMCIA cards supported by the "Hermes" (aka
orinoco) driver when used in PLX9052 based PCI adaptors. These
adaptors are not a full PCMCIA controller but act as a more limited
PCI <-> PCMCIA bridge. Several vendors sell such adaptors so that
802.11b PCMCIA cards can be used in desktop machines. The Netgear
MA301 is such an adaptor.
config TMD_HERMES
tristate "Hermes in TMD7160 based PCI adaptor support"
depends on PCI && HERMES
help
Enable support for PCMCIA cards supported by the "Hermes" (aka
orinoco) driver when used in TMD7160 based PCI adaptors. These
adaptors are not a full PCMCIA controller but act as a more limited
PCI <-> PCMCIA bridge. Several vendors sell such adaptors so that
802.11b PCMCIA cards can be used in desktop machines.
config NORTEL_HERMES
tristate "Nortel emobility PCI adaptor support"
depends on PCI && HERMES
help
Enable support for PCMCIA cards supported by the "Hermes" (aka
orinoco) driver when used in Nortel emobility PCI adaptors. These
adaptors are not full PCMCIA controllers, but act as a more limited
PCI <-> PCMCIA bridge.
config PCI_HERMES
tristate "Prism 2.5 PCI 802.11b adaptor support"
depends on PCI && HERMES
help
Enable support for PCI and mini-PCI 802.11b wireless NICs based on
the Prism 2.5 chipset. These are true PCI cards, not the 802.11b
PCMCIA cards bundled with PCI<->PCMCIA adaptors which are also
common. Some of the built-in wireless adaptors in laptops are of
this variety.
config PCMCIA_HERMES
tristate "Hermes PCMCIA card support"
depends on PCMCIA && HERMES
---help---
A driver for "Hermes" chipset based PCMCIA wireless adaptors, such
as the Lucent WavelanIEEE/Orinoco cards and their OEM (Cabletron/
EnteraSys RoamAbout 802.11, ELSA Airlancer, Melco Buffalo and
others). It should also be usable on various Prism II based cards
such as the Linksys, D-Link and Farallon Skyline. It should also
work on Symbol cards such as the 3Com AirConnect and Ericsson WLAN.
You will very likely need the Wireless Tools in order to
configure your card and that /etc/pcmcia/wireless.opts works:
<http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Tools.html>.
config PCMCIA_SPECTRUM
tristate "Symbol Spectrum24 Trilogy PCMCIA card support"
depends on PCMCIA && HERMES
select FW_LOADER
---help---
This is a driver for 802.11b cards using RAM-loadable Symbol
firmware, such as Symbol Wireless Networker LA4100, CompactFlash
cards by Socket Communications and Intel PRO/Wireless 2011B.
This driver requires firmware download on startup. Utilities
for downloading Symbol firmware are available at
<http://sourceforge.net/projects/orinoco/>
config ATMEL
tristate "Atmel at76c50x chipset 802.11b support"
depends on (PCI || PCMCIA) && WLAN_80211
select WIRELESS_EXT
select FW_LOADER
select CRC32
---help---
A driver 802.11b wireless cards based on the Atmel fast-vnet
chips. This driver supports standard Linux wireless extensions.
Many cards based on this chipset do not have flash memory
and need their firmware loaded at start-up. If yours is
one of these, you will need to provide a firmware image
to be loaded into the card by the driver. The Atmel
firmware package can be downloaded from
<http://www.thekelleys.org.uk/atmel>
config PCI_ATMEL
tristate "Atmel at76c506 PCI cards"
depends on ATMEL && PCI
---help---
Enable support for PCI and mini-PCI cards containing the
Atmel at76c506 chip.
config PCMCIA_ATMEL
tristate "Atmel at76c502/at76c504 PCMCIA cards"
depends on ATMEL && PCMCIA
select WIRELESS_EXT
select FW_LOADER
select CRC32
---help---
Enable support for PCMCIA cards containing the
Atmel at76c502 and at76c504 chips.
config AIRO_CS
tristate "Cisco/Aironet 34X/35X/4500/4800 PCMCIA cards"
depends on PCMCIA && (BROKEN || !M32R) && WLAN_80211
select WIRELESS_EXT
select CRYPTO
select CRYPTO_AES
---help---
This is the standard Linux driver to support Cisco/Aironet PCMCIA
802.11 wireless cards. This driver is the same as the Aironet
driver part of the Linux Pcmcia package.
It supports the new 802.11b cards from Cisco (Cisco 34X, Cisco 35X
- with or without encryption) as well as card before the Cisco
acquisition (Aironet 4500, Aironet 4800, Aironet 4800B). It also
supports OEM of Cisco such as the DELL TrueMobile 4800 and Xircom
802.11b cards.
This driver support both the standard Linux Wireless Extensions
and Cisco proprietary API, so both the Linux Wireless Tools and the
Cisco Linux utilities can be used to configure the card.
config PCMCIA_WL3501
tristate "Planet WL3501 PCMCIA cards"
depends on EXPERIMENTAL && PCMCIA && WLAN_80211
select WIRELESS_EXT
---help---
A driver for WL3501 PCMCIA 802.11 wireless cards made by Planet.
It has basic support for Linux wireless extensions and initial
micro support for ethtool.
config PRISM54
tristate 'Intersil Prism GT/Duette/Indigo PCI/Cardbus'
depends on PCI && EXPERIMENTAL && WLAN_80211
select WIRELESS_EXT
select FW_LOADER
---help---
Enable PCI and Cardbus support for the following chipset based cards:
ISL3880 - Prism GT 802.11 b/g
ISL3877 - Prism Indigo 802.11 a
ISL3890 - Prism Duette 802.11 a/b/g
For a complete list of supported cards visit <http://prism54.org>.
Here is the latest confirmed list of supported cards:
3com OfficeConnect 11g Cardbus Card aka 3CRWE154G72 (version 1)
Allnet ALL0271 PCI Card
Compex WL54G Cardbus Card
Corega CG-WLCB54GT Cardbus Card
D-Link Air Plus Xtreme G A1 Cardbus Card aka DWL-g650
I-O Data WN-G54/CB Cardbus Card
Kobishi XG-300 aka Z-Com Cardbus Card
Netgear WG511 Cardbus Card
Ovislink WL-5400PCI PCI Card
Peabird WLG-PCI PCI Card
Sitecom WL-100i Cardbus Card
Sitecom WL-110i PCI Card
SMC2802W - EZ Connect g 2.4GHz 54 Mbps Wireless PCI Card
SMC2835W - EZ Connect g 2.4GHz 54 Mbps Wireless Cardbus Card
SMC2835W-V2 - EZ Connect g 2.4GHz 54 Mbps Wireless Cardbus Card
Z-Com XG-900 PCI Card
Zyxel G-100 Cardbus Card
If you enable this you will need a firmware file as well.
You will need to copy this to /usr/lib/hotplug/firmware/isl3890.
You can get this non-GPL'd firmware file from the Prism54 project page:
<http://prism54.org>
You will also need the /etc/hotplug/firmware.agent script from
a current hotplug package.
Note: You need a motherboard with DMA support to use any of these cards
If you want to compile the driver as a module ( = code which can be
inserted in and removed from the running kernel whenever you want),
say M here and read <file:Documentation/kbuild/modules.txt>.
The module will be called prism54.ko.
config USB_ZD1201
tristate "USB ZD1201 based Wireless device support"
depends on USB && WLAN_80211
select WIRELESS_EXT
select FW_LOADER
---help---
Say Y if you want to use wireless LAN adapters based on the ZyDAS
ZD1201 chip.
This driver makes the adapter appear as a normal Ethernet interface,
typically on wlan0.
The zd1201 device requires external firmware to be loaded.
This can be found at http://linux-lc100020.sourceforge.net/
To compile this driver as a module, choose M here: the
module will be called zd1201.
config USB_NET_RNDIS_WLAN
tristate "Wireless RNDIS USB support"
depends on USB && WLAN_80211 && EXPERIMENTAL
select USB_USBNET
select USB_NET_CDCETHER
select USB_NET_RNDIS_HOST
select WIRELESS_EXT
---help---
This is a driver for wireless RNDIS devices.
These are USB based adapters found in devices such as:
Buffalo WLI-U2-KG125S
U.S. Robotics USR5421
Belkin F5D7051
Linksys WUSB54GSv2
Linksys WUSB54GSC
Asus WL169gE
Eminent EM4045
BT Voyager 1055
Linksys WUSB54GSv1
U.S. Robotics USR5420
BUFFALO WLI-USB-G54
All of these devices are based on Broadcom 4320 chip which is the
only wireless RNDIS chip known to date.
If you choose to build a module, it'll be called rndis_wlan.
config RTL8180
tristate "Realtek 8180/8185 PCI support"
depends on MAC80211 && PCI && WLAN_80211 && EXPERIMENTAL
select EEPROM_93CX6
---help---
This is a driver for RTL8180 and RTL8185 based cards.
These are PCI based chips found in cards such as:
(RTL8185 802.11g)
A-Link WL54PC
(RTL8180 802.11b)
Belkin F5D6020 v3
Belkin F5D6020 v3
Dlink DWL-610
Dlink DWL-510
Netgear MA521
Level-One WPC-0101
Acer Aspire 1357 LMi
VCTnet PC-11B1
Ovislink AirLive WL-1120PCM
Mentor WL-PCI
Linksys WPC11 v4
TrendNET TEW-288PI
D-Link DWL-520 Rev D
Repotec RP-WP7126
TP-Link TL-WN250/251
Zonet ZEW1000
Longshine LCS-8031-R
HomeLine HLW-PCC200
GigaFast WF721-AEX
Planet WL-3553
Encore ENLWI-PCI1-NT
TrendNET TEW-266PC
Gigabyte GN-WLMR101
Siemens-fujitsu Amilo D1840W
Edimax EW-7126
PheeNet WL-11PCIR
Tonze PC-2100T
Planet WL-8303
Dlink DWL-650 v M1
Edimax EW-7106
Q-Tec 770WC
Topcom Skyr@cer 4011b
Roper FreeLan 802.11b (edition 2004)
Wistron Neweb Corp CB-200B
Pentagram HorNET
QTec 775WC
TwinMOS Booming B Series
Micronet SP906BB
Sweex LC700010
Surecom EP-9428
Safecom SWLCR-1100
Thanks to Realtek for their support!
config RTL8187
tristate "Realtek 8187 USB support"
depends on MAC80211 && USB && WLAN_80211 && EXPERIMENTAL
select EEPROM_93CX6
---help---
This is a driver for RTL8187 based cards.
These are USB based chips found in cards such as:
Netgear WG111v2
Thanks to Realtek for their support!
config ADM8211
tristate "ADMtek ADM8211 support"
depends on MAC80211 && PCI && WLAN_80211 && EXPERIMENTAL
select CRC32
select EEPROM_93CX6
---help---
This driver is for ADM8211A, ADM8211B, and ADM8211C based cards.
These are PCI/mini-PCI/Cardbus 802.11b chips found in cards such as:
Xterasys Cardbus XN-2411b
Blitz NetWave Point PC
TrendNet 221pc
Belkin F5D6001
SMC 2635W
Linksys WPC11 v1
Fiberline FL-WL-200X
3com Office Connect (3CRSHPW796)
Corega WLPCIB-11
SMC 2602W V2 EU
D-Link DWL-520 Revision C
However, some of these cards have been replaced with other chips
like the RTL8180L (Xterasys Cardbus XN-2411b, Belkin F5D6001) or
the Ralink RT2400 (SMC2635W) without a model number change.
Thanks to Infineon-ADMtek for their support of this driver.
config MAC80211_HWSIM
tristate "Simulated radio testing tool for mac80211"
depends on MAC80211 && WLAN_80211
---help---
This driver is a developer testing tool that can be used to test
IEEE 802.11 networking stack (mac80211) functionality. This is not
needed for normal wireless LAN usage and is only for testing. See
Documentation/networking/mac80211_hwsim for more information on how
to use this tool.
To compile this driver as a module, choose M here: the module will be
called mac80211_hwsim. If unsure, say N.
source "drivers/net/wireless/p54/Kconfig"
source "drivers/net/wireless/ath5k/Kconfig"
source "drivers/net/wireless/iwlwifi/Kconfig"
source "drivers/net/wireless/hostap/Kconfig"
source "drivers/net/wireless/b43/Kconfig"
source "drivers/net/wireless/b43legacy/Kconfig"
source "drivers/net/wireless/zd1211rw/Kconfig"
source "drivers/net/wireless/rt2x00/Kconfig"
endmenu