On Fri, Nov 09, 2012 at 05:00:54PM +0100, Christian König wrote:
> On 09.11.2012 16:45, Rafał Miłecki wrote:
> >2012/11/9 Thierry Reding <thierry.reding@xxxxxxxxxxxxxxxxx>:
> >>+/* all fields little endian */
> >>+struct hdmi_audio_infoframe {
> >>+ /* PB0 */
> >>+ u8 csum;
> >>+
> >>+ /* PB1 */
> >>+ unsigned cc:3; /* channel count */
> >>+ unsigned res1:1;
> >>+ unsigned ct:4; /* coding type */
> >>+
> >>+ /* PB2 */
> >>+ unsigned ss:2; /* sample size */
> >>+ unsigned sf:3; /* sample frequency */
> >>+ unsigned res2:3;
> >>+
> >>+ /* PB3 */
> >>+ unsigned cxt:5; /* coding extention type */
> >>+ unsigned res3:3;
> >>+
> >>+ /* PB4 */
> >>+ u8 ca; /* channel/speaker allocation */
> >>+
> >>+ /* PB5 */
> >>+ unsigned res5:3;
> >>+ unsigned lsv:4; /* level shift value */
> >>+ unsigned dm_inh:1; /* downmix inhibit */
> >>+
> >>+ /* PB6-10 reserved */
> >>+ u8 res6;
> >>+ u8 res7;
> >>+ u8 res8;
> >>+ u8 res9;
> >>+ u8 res10;
> >>+} __packed;
> >I was told it won't work on different endian devices. See
> >[RFC][PATCH] drm/radeon/hdmi: define struct for AVI infoframe
> >http://lists.freedesktop.org/archives/dri-devel/2012-May/022544.html
>
> Yeah, that's indeed true. And honestly adding just another
> implementation of the HDMI info frames sounds like somebody should
> finally sit down and implement it in a common drm_hdmi.c
So I've been looking at what most other implementations do and it seems
a lot just fill the AVI infoframe with zeroes while only a few actually
try to put useful information in them. Still in order to plan for a
generic solution, I thought maybe something like the below set of
structures and functions could work:
/*
* Structure that contains the infoframe fields in a form that allows them to
* be easily accessed from C code.
*/
struct hdmi_avi_infoframe;
/*
* DRM helper to fill a struct hdmi_avi_infoframe with information taken from
* a struct drm_display_mode. Fields that cannot automatically be derived by
* looking at a struct drm_display_mode are set to the default values.
*/
int drm_hdmi_avi_infoframe_from_display_mode(struct hdmi_avi_infoframe *frame,
struct drm_display_mode *mode);
/*
* Packs the struct hdmi_avi_infoframe into a binary buffer that can be
* programmed to the hardware-specific registers.
*/
ssize_t hdmi_avi_infoframe_pack(struct hdmi_avi_infoframe *frame,
void *buffer, size_t size);
Such a scheme would allow DRM drivers to call the helper and tweak the
fields in the structure if the want or need to and call the packing
function to obtain a buffer that they can write to the controller.
Does that sound at all reasonable?
Thierry
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