Re: [PATCH libdrm] xf86drm: introduce drmGetDeviceNameFromFd2

["Nicolai Hähnle" <nhaehnle@gmail.com>]

On 10.11.2016 18:43, Emil Velikov wrote:
> From: Emil Velikov <emil.velikov@collabora.com>
>
> The original version considered only card devices, while this will pick
> the device/node name regardless - card, control, renderD, other...
>
> Current implementation is "linux" specific, in such that it relies on
> sysfs/uevent file. At the same time this gives us the flexibility to
> support any nodes even future ones, as long as they're within DRM_MAJOR.
>
> Shamelessly copied from mesa, latter by: Gary Wong <gtw@gnu.org>
> Signed-off-by: Emil Velikov <emil.velikov@collabora.com>

Makes sense to me.

Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>

> ---
> There's quite a bit of [subtle chaos] in mesa about this. Sometimes we
> explicitly request the render node, sometimes we use an open-coded version
> of drmGetDeviceNameFromFd, which due to sheer luck just works.
>
> One could apply some polish here, but I'd choose to keep things as close
> to original.
> ---
>  xf86drm.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  xf86drm.h |  5 +++++
>  2 files changed, 56 insertions(+)
>
> diff --git a/xf86drm.c b/xf86drm.c
> index 80e2f27..0bca43a 100644
> --- a/xf86drm.c
> +++ b/xf86drm.c
> @@ -3367,3 +3367,54 @@ free_locals:
>      free(local_devices);
>      return ret;
>  }
> +
> +char *drmGetDeviceNameFromFd2(int fd)
> +{
> +#ifdef __linux__
> +    struct stat sbuf;
> +    char *device_name = NULL;
> +    unsigned int maj, min;
> +    FILE *f;
> +    char buf[512];
> +    static const char match[9] = "\nDEVNAME=";
> +    int expected = 1;
> +
> +
> +    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;
> +
> +    snprintf(buf, sizeof(buf), "/sys/dev/char/%d:%d/uevent", maj, min);
> +    if (!(f = fopen(buf, "r")))
> +        return NULL;
> +
> +    while (expected < sizeof(match)) {
> +        int c = getc(f);
> +
> +        if (c == EOF) {
> +            fclose(f);
> +            return NULL;
> +        } else if (c == match[expected] )
> +            expected++;
> +        else
> +            expected = 0;
> +    }
> +
> +    strcpy(buf, "/dev/");
> +    if (fgets(buf + 5, sizeof(buf) - 5, f)) {
> +        buf[strcspn(buf, "\n")] = '\0';
> +        device_name = strdup(buf);
> +    }
> +
> +    fclose(f);
> +    return device_name;
> +#else
> +#warning "Missing implementation of drmGetDeviceNameFromFd2"
> +    return NULL;
> +#endif
> +}
> diff --git a/xf86drm.h b/xf86drm.h
> index d1ebc32..4fa395e 100644
> --- a/xf86drm.h
> +++ b/xf86drm.h
> @@ -753,6 +753,11 @@ typedef struct _drmEventContext {
>  extern int drmHandleEvent(int fd, drmEventContextPtr evctx);
>
>  extern char *drmGetDeviceNameFromFd(int fd);
> +
> +/* Improved version of drmGetDeviceNameFromFd which attributes for any type of
> + * device/node - card, control or renderD.
> + */
> +extern char *drmGetDeviceNameFromFd2(int fd);
>  extern int drmGetNodeTypeFromFd(int fd);
>
>  extern int drmPrimeHandleToFD(int fd, uint32_t handle, uint32_t flags, int *prime_fd);
>
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