Hi, On Tuesday 21 April 2009 03:47:34 Ming Lei wrote: > 2009/4/21 Laurent Pinchart <laurent.pinchart@xxxxxxxxx>: > > On Saturday 18 April 2009 06:51:11 leiming wrote: > >> On Fri, 17 Apr 2009 19:55:29 -0700 (PDT) > >> > >> Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > >> > > @@ -742,7 +742,7 @@ static int uvc_alloc_urb_buffers(struct > >> > > uvc_video_device *video, > >> > > /* Buffers are already allocated, bail out. */ > >> > > if (video->urb_size) > >> > > - return 0; > >> > > + return DIV_ROUND_UP(video->urb_size, psize); > >> > > >> > I don't think this is right. It should round _down_. > >> > > >> > It's supposed to return 'npackets', but if you pass it a different > >> > packet size than it was passed originally, it can now return a > >> > potentially bigger number than the already allocated buffer, no? > >> > > >> > So I think it should round down (ie use a regular divide). No? > >> > >> Yes,you are correct, please ignore my last reply, and following is > >> the fixed patch. > > > > psize and video->urb_size shouldn't have changed before and after resume, > > otherwise we'll get into trouble anyway. A regular divide and a round-up > > divide should then return the same result. I'll take the regular divide, > > as it will be more efficient. > > Yes. > > >> Thanks. > >> > >> From a3b3d72cdd57a0699fb643b41b78eb7beb211ff5 Mon Sep 17 00:00:00 2001 > >> From: Ming Lei <tom.leiming@xxxxxxxxx> > >> Date: Wed, 15 Apr 2009 22:32:51 +0800 > >> Subject: [PATCH] V4L/DVB:usbvideo:fix uvc resume failed(v2) > >> > >> Now urb buffers is not freed before suspend, so uvc_alloc_urb_buffers > >> should return packet counts allocated originally during uvc resume > >> , instead of zero. > >> > >> This version uses round down to return packet counts on Linus's > >> suggestions, or else may lead to buffer destructed if packet size > >> is changed before calling uvc_alloc_urb_buffers() in this kind of > >> case. > > > > The comment is misleading. If the packet size changes we need to > > reallocate the buffers anyway. Have you checked if the packet size (which > > depends on the endpoint being selected) can be changed between suspend > > and resume, either by the uvcvideo driver (I don't think it can) or the > > USB core ? > > The packet size does not change between suspend and resume. I mean > uvc_alloc_urb_buffers() still can be used in other cases if buffers was not > freed and is reuesed in future. It seems there is no such cases in uvcvideo > now, but uvc_alloc_urb_buffers() really __can__ work in such case, isn't it? > > IMHO It is only used to allocate or reserve UVC_URBS usb buffers, which size > is video->urb_size, and npackets can be shortened or enlarged if psize is > changed, after all. You're right. Patch applied, thanks. Best regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
