Hi, Jonathan
>-----Original Message----- >From: Jonathan Corbet [mailto:cor...@lwn.net] >Sent: Monday, 17 December, 2012 00:56 >To: Albert Wang >Cc: g.liakhovet...@gmx.de; linux-media@vger.kernel.org; Libin Yang >Subject: Re: [PATCH V3 15/15] [media] marvell-ccic: add 3 frame buffers >support in >DMA_CONTIG mode > >On Sat, 15 Dec 2012 17:58:04 +0800 >Albert Wang <twan...@marvell.com> wrote: > >> This patch adds support of 3 frame buffers in DMA-contiguous mode. >> >> In current DMA_CONTIG mode, only 2 frame buffers can be supported. >> Actually, Marvell CCIC can support at most 3 frame buffers. >> >> Currently 2 frame buffers mode will be used by default. >> To use 3 frame buffers mode, can do: >> define MAX_FRAME_BUFS 3 >> in mcam-core.h > >Now that the code supports three buffers properly, is there any reason not >to use that mode by default? > [Albert Wang] Because the original code use the two buffers mode, so we keep it. :) >Did you test that it works properly if allocation of the third buffer fails? > [Albert Wang] Yes, we test it in our Marvell platforms. >Otherwise looks OK except for one thing: > >> diff --git a/drivers/media/platform/marvell-ccic/mcam-core.h >b/drivers/media/platform/marvell-ccic/mcam-core.h >> index 765d47c..9bf31c8 100755 >> --- a/drivers/media/platform/marvell-ccic/mcam-core.h >> +++ b/drivers/media/platform/marvell-ccic/mcam-core.h >> @@ -62,6 +62,13 @@ enum mcam_state { >> #define MAX_DMA_BUFS 3 >> >> /* >> + * CCIC can support at most 3 frame buffers in DMA_CONTIG buffer mode >> + * 2 - Use Two Buffers mode >> + * 3 - Use Three Buffers mode >> + */ >> +#define MAX_FRAME_BUFS 2 /* Current marvell-ccic used Two Buffers mode */ >> + >> +/* >> * Different platforms work best with different buffer modes, so we >> * let the platform pick. >> */ >> @@ -99,6 +106,10 @@ struct mcam_frame_state { >> unsigned int frames; >> unsigned int singles; >> unsigned int delivered; >> + /* >> + * Only usebufs == 2 can enter single buffer mode >> + */ >> + unsigned int usebufs; >> }; > >What is the purpose of the "usebufs" field? The code maintains it in >various places, but I don't see anywhere that actually uses that value for >anything. > [Albert Wang] Two buffers mode doesn't need it. But Three buffers mode need it indicates which conditions we need set the single buffer flag. I used "tribufs" as the name in the previous version, but it looks it's a confused name when we merged Two buffers mode and Three buffers mode with same code by removing #ifdef based on your comments months ago. :) So we just changed the name with "usebufs". >Thanks, > >jon Thanks Albert Wang 86-21-61092656 -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
