[PATCH libdrm 1/5] xf86drm: implement drmGetMinorNameForFD for non-sysfs

[Emil Velikov]

On 26 November 2016 at 00:40, Jonathan Gray <jsg at jsg.id.au> wrote:
> Implement drmGetMinorNameForFD for systems without sysfs by
> adapting drm_get_device_name_for_fd() from the Mesa loader.
>
> Signed-off-by: Jonathan Gray <jsg at jsg.id.au>
> ---
>  xf86drm.c | 20 +++++++++++++++++++-
>  1 file changed, 19 insertions(+), 1 deletion(-)
>
> diff --git a/xf86drm.c b/xf86drm.c
> index ed924a7..216220c 100644
> --- a/xf86drm.c
> +++ b/xf86drm.c
> @@ -2818,7 +2818,25 @@ static char *drmGetMinorNameForFD(int fd, int type)
>  out_close_dir:
>      closedir(sysdir);
>  #else
> -#warning "Missing implementation of drmGetMinorNameForFD"
> +    struct stat sbuf;
> +    unsigned int maj, min;
> +    char buf[PATH_MAX + 1];
> +    int n;
> +
> +    if (fstat(fd, &sbuf))
> +        return NULL;
> +
> +    maj = major(sbuf.st_rdev);
> +    min = minor(sbuf.st_rdev);
> +
> +    if (maj != DRM_MAJOR || !S_ISCHR(sbuf.st_mode))
> +        return NULL;
> +
> +    n = snprintf(buf, sizeof(buf), DRM_DEV_NAME, DRM_DIR_NAME, min);
> +    if (n == -1 || n >= sizeof(buf))
> +        return NULL;
> +
> +    return strdup(buf);
Doesn't look too good I'm afraid:
 - you ignore the node type, making the whole helper and API that
depends on it useless.
Note: mesa wants to know the render node name for the given fd. We can
replace with drmGetDevice but I'd like to check the double-auth [and
related fun] trimming things down before changing things.

 - implementation seems identical to drmGetDeviceNameFromFd(). Barring
a few trivial bits of course.
Speaking of which there is drmGetDeviceNameFromFd2 which attributes
for any node type(s) - the present primary, control and render plus
any future ones.
I'm leaning towards using it in the next (or one after) version in mesa.

Have you and fellow OpenBSD developers considered render nodes. Do you
have any preliminary ideas how it will be exposed, such that you can
build a comprehensive interface here ?

Thanks
Emil