On 16 September 2015 at 02:25, Rob Herring [off-list ref] wrote:
Hi Rob, thanks a lot for reply:-)

On 09/15/2015 04:37 AM, Xinwei Kong wrote:

quoted

If you config DRM_HISI_FBDEV optional, this patch will only support fbdev
mode while also supporting double buffer.

This is a lot of duplicated code from CMA fbdev. Is double buffering the
only reason why CMA fbdev can't be used or are there some other
constraints?

Yes, double buffering is the main reason we rewrite our own fbdev.
CMA fbdev only create one buffer. But we need at least  double buffer for
running Android with fbdev.

Double buffering in fbdev has always been a hack, so I'm

guessing that is not a feature that should be added here.

If so, I think it is hard to be accepted for my cma fbdev patch to support

multi buffer.
This early week, I have sent a cma fbdev patch for supporting this. The
subject is
"[PATCH] drm/cma-helper: Add multi buffer support for cma fbdev".
We do have a strong will to support this feature. I described the reason in
the patch. Please take a look for me. Thank you very much.

-Xinliang

Rob

quoted

Signed-off-by: Xinliang Liu <xinliang.liu@linaro.org>
Signed-off-by: Xinwei Kong <kong.kongxinwei@hisilicon.com>
Signed-off-by: Andy Green <redacted>
Signed-off-by: Jiwen Qi <redacted>
Signed-off-by: Yu Gong <redacted>
---
 drivers/gpu/drm/hisilicon/Kconfig              |  13 +
 drivers/gpu/drm/hisilicon/Makefile             |   3 +-
 drivers/gpu/drm/hisilicon/hisi_drm_connector.c |   4 +
 drivers/gpu/drm/hisilicon/hisi_drm_drv.c       |   9 +
 drivers/gpu/drm/hisilicon/hisi_drm_dsi.c       |  15 +
 drivers/gpu/drm/hisilicon/hisi_drm_fb.h        |   5 +
 drivers/gpu/drm/hisilicon/hisi_drm_fbdev.c     | 395

+++++++++++++++++++++++++

quoted

 drivers/gpu/drm/hisilicon/hisi_drm_fbdev.h     |  24 ++
 8 files changed, 467 insertions(+), 1 deletion(-)
 create mode 100644 drivers/gpu/drm/hisilicon/hisi_drm_fbdev.c
 create mode 100644 drivers/gpu/drm/hisilicon/hisi_drm_fbdev.h