Current cvt timing calculation supports reduced blanking (RB) version 1. This patch adds the support for RB version 2, which was missing. Compared to RB version 1, RB version 2 differs on different parameters. This difference is summarized in the document VESA Coordinated Video Timings Standard Version 1.2, Page 24, Table 5-4: Delta between Original Reduced Blank Timing and Reduced Blank Timing V2.
One of the key difference to note is related to vsync parameter. Normally vsync pulse duration varies based on aspect ratio. v4l2_detect_cvt() makes use of this fact and infers the apsect ratio from vsync. However, in case of RB version 2, one cannot infer aspect ratio from vsync because for RB version 2 standard uses fixed value of vsync = 8 irrespective of aspect ratio. In fact, vsync = 8 is used to indicate the timings are based RB version 2. As such RB version 2 allows for non standard aspect ratios and it needs to be calculated from image height and width. Referring to input parameters available to v4l2_detect_cvt(), it does not have infromation about width. It rather have information about height and the function calculates width after it infers about aspect ratio from vsync. For RB version 2, this needs to be changed, possibly, by supplying aspect ratio to v4l2_detect_cvt(). (on the lines similar to that of detect_gtf()) I have not done any API change in this patch. This patch is rather limited to changes in timing calculation for RB version 2. As of now, I have just assumed a default value for aspect ratio at 16:9. Please review the timing calculation part and share your comments. Also share your suggestions, comments about if we should extend v4l2_detect_cvt() api to include aspect ratio. Regards, Prashant Prashant Laddha (1): v4l2-dv-timings: add support for reduced blanking v2 drivers/media/v4l2-core/v4l2-dv-timings.c | 72 +++++++++++++++++++++++-------- 1 file changed, 54 insertions(+), 18 deletions(-) -- 1.9.1 -- 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
