Re: [git:v4l-dvb/for_v3.1] [media] uvcvideo: Add FIX_BANDWIDTH quirk to HP Webcam on HP Mini 5103 netbook

[Mauro Carvalho Chehab <mchehab@redhat.com>]

Em 28-07-2011 08:42, Kirill Smelkov escreveu:
> On Wed, Jul 27, 2011 at 09:42:08PM +0200, Mauro Carvalho Chehab wrote:
>> This is an automatic generated email to let you know that the following patch were queued at the 
>> http://git.linuxtv.org/media_tree.git tree:
>>
>> Subject: [media] uvcvideo: Add FIX_BANDWIDTH quirk to HP Webcam on HP Mini 5103 netbook
>> Author:  Kirill Smelkov <kirr@mns.spb.ru>
>> Date:    Fri Jul 22 11:47:22 2011 -0300
> 
> Thanks
> 
> 
>> The camera there identifies itself as being manufactured by Cheng Uei
>> Precision Industry Co., Ltd (Foxlink), and product is titled as "HP
>> Webcam [2 MP Fixed]".
>>
>> I was trying to get 2 USB video capture devices to work simultaneously,
>> and noticed that the above mentioned webcam always requires packet size
>> = 3072 bytes per micro frame (~= 23.4 MB/s isoc bandwidth), which is far
>> more than enough to get standard NTSC 640x480x2x30 = ~17.6 MB/s isoc
>> bandwidth.
>>
>> As there are alt interfaces with smaller MxPS
>>
>>     T:  Bus=01 Lev=01 Prnt=01 Port=03 Cnt=01 Dev#=  2 Spd=480  MxCh= 0
>>     D:  Ver= 2.00 Cls=ef(misc ) Sub=02 Prot=01 MxPS=64 #Cfgs=  1
>>     P:  Vendor=05c8 ProdID=0403 Rev= 1.06
>>     S:  Manufacturer=Foxlink
>>     S:  Product=HP Webcam [2 MP Fixed]
>>     S:  SerialNumber=200909240102
>>     C:* #Ifs= 2 Cfg#= 1 Atr=80 MxPwr=500mA
>>     A:  FirstIf#= 0 IfCount= 2 Cls=0e(video) Sub=03 Prot=00
>>     I:* If#= 0 Alt= 0 #EPs= 1 Cls=0e(video) Sub=01 Prot=00 Driver=uvcvideo
>>     E:  Ad=83(I) Atr=03(Int.) MxPS=  16 Ivl=4ms
>>     I:* If#= 1 Alt= 0 #EPs= 0 Cls=0e(video) Sub=02 Prot=00 Driver=uvcvideo
>>     I:  If#= 1 Alt= 1 #EPs= 1 Cls=0e(video) Sub=02 Prot=00 Driver=uvcvideo
>>     E:  Ad=81(I) Atr=05(Isoc) MxPS= 128 Ivl=125us
>>     I:  If#= 1 Alt= 2 #EPs= 1 Cls=0e(video) Sub=02 Prot=00 Driver=uvcvideo
>>     E:  Ad=81(I) Atr=05(Isoc) MxPS= 512 Ivl=125us
>>     I:  If#= 1 Alt= 3 #EPs= 1 Cls=0e(video) Sub=02 Prot=00 Driver=uvcvideo
>>     E:  Ad=81(I) Atr=05(Isoc) MxPS=1024 Ivl=125us
>>     I:  If#= 1 Alt= 4 #EPs= 1 Cls=0e(video) Sub=02 Prot=00 Driver=uvcvideo
>>     E:  Ad=81(I) Atr=05(Isoc) MxPS=1536 Ivl=125us
>>     I:  If#= 1 Alt= 5 #EPs= 1 Cls=0e(video) Sub=02 Prot=00 Driver=uvcvideo
>>     E:  Ad=81(I) Atr=05(Isoc) MxPS=2048 Ivl=125us
>>     I:  If#= 1 Alt= 6 #EPs= 1 Cls=0e(video) Sub=02 Prot=00 Driver=uvcvideo
>>     E:  Ad=81(I) Atr=05(Isoc) MxPS=2688 Ivl=125us
>>     I:  If#= 1 Alt= 7 #EPs= 1 Cls=0e(video) Sub=02 Prot=00 Driver=uvcvideo
>>     E:  Ad=81(I) Atr=05(Isoc) MxPS=3072 Ivl=125us
>>
>> UVC_QUIRK_FIX_BANDWIDTH helps here and NTSC video can be served with
>> MxPS=2688 i.e. 20.5 MB/s isoc bandwidth.
>>
>> In terms of microframe time allocation, before the quirk NTSC video
>> required 60 usecs / microframe and 53 usecs / microframe after.
>>
>> Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>> Signed-off-by: Kirill Smelkov <kirr@mns.spb.ru>
>> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
> 
> 
> May I ask, why you removed the reference to cc62a7eb? Original patch
> description contained the following paragraph just before sob
> 
>     Now with tweaked ehci-hcd to allow up to 90% isoc bandwidth (cc62a7eb
>     "USB: EHCI: Allow users to override 80% max periodic bandwidth") I can
>     capture two video sources -- PAL 720x576 YUV422 @25fps + NTSC 640x480
>     YUV422 @30fps simultaneously.  Hooray!
> 
> 
> which was removed on applying.

For a few reasons:
1) I was not sure if the changeset reference was not changed when
   merged upstream, and I was too lazy^Wbusy to double check ;)
2) Reducing the amount of bandwidth used is good, even without trying to use
   two webcams;
3) The bandwidth override patch is independent of this one.

Regards,
Mauro