Dne 29.1.2019 v 19:44 Takashi Iwai napsal(a):
> On Tue, 29 Jan 2019 18:59:07 +0100,
> Jaroslav Kysela wrote:
>>
>> This patch implements new SNDRV_PCM_IOCTL_ANONYMOUS_DUP ioctl which
>> returns the new duplicated anonymous inode file descriptor
>> (anon_inode:snd-pcm) which can be passed to the restricted clients.
>>
>> This patch is meant to be the alternative for the dma-buf interface. Both
>> implementation have some pros and cons:
>>
>> anon_inode:dmabuf
>>
>> - a bit standard export API for the DMA buffers
>> - fencing for the concurrent access [1]
>> - driver/kernel interface for the DMA buffer [1]
>> - multiple attach/detach scheme [1]
>>
>> [1] the real usage for the sound PCM is unknown at the moment for this feature
>>
>> anon_inode:snd-pcm
>>
>> - simple (no problem with ref-counting, non-standard mmap implementation etc.)
>> - allow to use more sound interfaces for the file descriptor like status ioctls
>> - more fine grained security policies (another anon_inode name unshared with
>> other drivers)
>
> Your sign-off seems missing.
Fixed now. Thanks.
>> @@ -999,15 +1002,19 @@ int snd_pcm_attach_substream(struct snd_pcm *pcm, int stream,
>> }
>>
>> if (file->f_flags & O_APPEND) {
>> - if (prefer_subdevice < 0) {
>> - if (pstr->substream_count > 1)
>> - return -EINVAL; /* must be unique */
>> - substream = pstr->substream;
>> + if (clone) {
>> + substream = clone;
>> } else {
>> - for (substream = pstr->substream; substream;
>> - substream = substream->next)
>> - if (substream->number == prefer_subdevice)
>> - break;
>> + if (prefer_subdevice < 0) {
>> + if (pstr->substream_count > 1)
>> + return -EINVAL; /* must be unique */
>> + substream = pstr->substream;
>> + } else {
>> + for (substream = pstr->substream; substream;
>> + substream = substream->next)
>> + if (substream->number == prefer_subdevice)
>> + break;
>> + }
>> }
>> if (! substream)
>> return -ENODEV;
>
> So the clone case should return via this block, then...
>
>> @@ -1018,11 +1025,18 @@ int snd_pcm_attach_substream(struct snd_pcm *pcm, int stream,
>> return 0;
>> }
>>
>> - for (substream = pstr->substream; substream; substream = substream->next) {
>> - if (!SUBSTREAM_BUSY(substream) &&
>> - (prefer_subdevice == -1 ||
>> - substream->number == prefer_subdevice))
>> - break;
>> + if (clone) {
>> + substream = clone;
>> + if (SUBSTREAM_BUSY(substream))
>> + return -EAGAIN;
>> + } else {
>> + for (substream = pstr->substream; substream;
>> + substream = substream->next) {
>> + if (!SUBSTREAM_BUSY(substream) &&
>> + (prefer_subdevice == -1 ||
>> + substream->number == prefer_subdevice))
>> + break;
>> + }
>
> ... do we need to support cloning without O_APPEND?
I think that it would be better to pass the subdevice number to
snd_pcm_attach_substream(). It will reduce the required modifications.
I will change this.
Thanks,
Jaroslav
--
Jaroslav Kysela <perex@xxxxxxxx>
Linux Sound Maintainer; ALSA Project; Red Hat, Inc.
_______________________________________________
Alsa-devel mailing list
Alsa-devel@xxxxxxxxxxxxxxxx
http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
