Hi Laurent,
On 06/11/2018 23:13, Laurent Pinchart wrote:
> Hi Kieran,
>
> Thank you for the patch.
>
> On Tuesday, 6 November 2018 23:27:19 EET Kieran Bingham wrote:
>> From: Kieran Bingham <kieran.bingham@xxxxxxxxxxxxxxxx>
>>
>> We have both uvc_init_video() and uvc_video_init() calls which can be
>> quite confusing to determine the process for each. Now that video
>> uvc_video_enable() has been renamed to uvc_video_start_streaming(),
>> adapt these calls to suit the new flow.
>>
>> Rename uvc_init_video() to uvc_video_start() and uvc_uninit_video() to
>> uvc_video_stop().
>
> I agree that these functions are badly named and should be renamed. We are
> however entering the nitpicking territory :-) The two functions do more that
> starting and stopping, they also allocate and free URBs and the associated
> buffers. It could also be argued that they don't actually start and stop
> anything, as beyond URB management, they just queue the URBs initially and
> kill them. I thus wonder if we could come up with better names.
Well the act of killing (poisoning now) the URBs will certainly stop the
stream, but I guess submitting the URBs isn't necessarily the key act to
starting the stream.
I believe that needs the interface to be set correctly, and the buffers
to be available?
Although - I've just double-checked uvc_{video_start,init_video}() and
that is indeed what it does?
- start stats
- Initialise endpoints
- Perform allocations
- Submit URBs
Am I missing something? Is there another step that is pivotal to
starting the USB packet/urb stream flow after this point ?
Is it not true that the USB stack will start processing data at
submitting URB completion callbacks after the end of uvc_video_start();
and will no longer process data at the end of uvc_video_stop() (and thus
no more completion callbacks)?
(That's a real question to verify my interpretation)
To me - these functions feel like the real 'start' and 'stop' components
of the data stream - hence my choice in naming.
Is your concern that you would like the functions to be more descriptive
over their other actions such as? :
uvc_video_initialise_start()
uvc_video_allocate_init_start()
Or something else? (I don't think those two are good names though)
--
Kieran
>> Signed-off-by: Kieran Bingham <kieran.bingham@xxxxxxxxxxxxxxxx>
>> ---
>> drivers/media/usb/uvc/uvc_video.c | 18 +++++++++---------
>> 1 file changed, 9 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/media/usb/uvc/uvc_video.c
>> b/drivers/media/usb/uvc/uvc_video.c index 0d35e933856a..020022e6ade4 100644
>> --- a/drivers/media/usb/uvc/uvc_video.c
>> +++ b/drivers/media/usb/uvc/uvc_video.c
>> @@ -1641,7 +1641,7 @@ static int uvc_alloc_urb_buffers(struct uvc_streaming
>> *stream, /*
>> * Uninitialize isochronous/bulk URBs and free transfer buffers.
>> */
>> -static void uvc_uninit_video(struct uvc_streaming *stream, int
>> free_buffers) +static void uvc_video_stop(struct uvc_streaming *stream, int
>> free_buffers) {
>> struct uvc_urb *uvc_urb;
>>
>> @@ -1718,7 +1718,7 @@ static int uvc_init_video_isoc(struct uvc_streaming
>> *stream,
>>
>> urb = usb_alloc_urb(npackets, gfp_flags);
>> if (urb == NULL) {
>> - uvc_uninit_video(stream, 1);
>> + uvc_video_stop(stream, 1);
>> return -ENOMEM;
>> }
>>
>> @@ -1786,7 +1786,7 @@ static int uvc_init_video_bulk(struct uvc_streaming
>> *stream,
>>
>> urb = usb_alloc_urb(0, gfp_flags);
>> if (urb == NULL) {
>> - uvc_uninit_video(stream, 1);
>> + uvc_video_stop(stream, 1);
>> return -ENOMEM;
>> }
>>
>> @@ -1806,7 +1806,7 @@ static int uvc_init_video_bulk(struct uvc_streaming
>> *stream, /*
>> * Initialize isochronous/bulk URBs and allocate transfer buffers.
>> */
>> -static int uvc_init_video(struct uvc_streaming *stream, gfp_t gfp_flags)
>> +static int uvc_video_start(struct uvc_streaming *stream, gfp_t gfp_flags)
>> {
>> struct usb_interface *intf = stream->intf;
>> struct usb_host_endpoint *ep;
>> @@ -1894,7 +1894,7 @@ static int uvc_init_video(struct uvc_streaming
>> *stream, gfp_t gfp_flags) if (ret < 0) {
>> uvc_printk(KERN_ERR, "Failed to submit URB %u "
>> "(%d).\n", i, ret);
>> - uvc_uninit_video(stream, 1);
>> + uvc_video_stop(stream, 1);
>> return ret;
>> }
>> }
>> @@ -1925,7 +1925,7 @@ int uvc_video_suspend(struct uvc_streaming *stream)
>> return 0;
>>
>> stream->frozen = 1;
>> - uvc_uninit_video(stream, 0);
>> + uvc_video_stop(stream, 0);
>> usb_set_interface(stream->dev->udev, stream->intfnum, 0);
>> return 0;
>> }
>> @@ -1961,7 +1961,7 @@ int uvc_video_resume(struct uvc_streaming *stream, int
>> reset) if (ret < 0)
>> return ret;
>>
>> - return uvc_init_video(stream, GFP_NOIO);
>> + return uvc_video_start(stream, GFP_NOIO);
>> }
>>
>> /* ------------------------------------------------------------------------
>> @@ -2095,7 +2095,7 @@ int uvc_video_start_streaming(struct uvc_streaming
>> *stream) if (ret < 0)
>> goto error_commit;
>>
>> - ret = uvc_init_video(stream, GFP_KERNEL);
>> + ret = uvc_video_start(stream, GFP_KERNEL);
>> if (ret < 0)
>> goto error_video;
>>
>> @@ -2111,7 +2111,7 @@ int uvc_video_start_streaming(struct uvc_streaming
>> *stream)
>>
>> int uvc_video_stop_streaming(struct uvc_streaming *stream)
>> {
>> - uvc_uninit_video(stream, 1);
>> + uvc_video_stop(stream, 1);
>> if (stream->intf->num_altsetting > 1) {
>> usb_set_interface(stream->dev->udev,
>> stream->intfnum, 0);
>
>
--
Regards
--
Kieran
