[Intel-gfx] [PATCH v6 3/4] drm: Expand max DRM device number to full MINORBITS

[James Zhu]

On 2023-07-24 17:14, Michał Winiarski wrote:
> Having a limit of 64 DRM devices is not good enough for modern world
> where we have multi-GPU servers, SR-IOV virtual functions and virtual
> devices used for testing.
> Let's utilize full minor range for DRM devices.
> To avoid regressing the existing userspace, we're still maintaining the
> numbering scheme where 0-63 is used for primary, 64-127 is reserved
> (formerly for control) and 128-191 is used for render.
> For minors >= 192, we're allocating minors dynamically on a first-come,
> first-served basis.

[JZ] Hello Michal,

Do you have libdrm patches for review together with this change?

Especially to support static int drmGetMinorType(int major, int minor).

Thanks and Best Regards!

James Zhu

>
> Signed-off-by: Michał Winiarski<michal.winiarski at intel.com>
> ---
>   drivers/gpu/drm/drm_drv.c | 12 ++++++++++++
>   1 file changed, 12 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index 34b60196c443..c2c6e80e6b31 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -121,10 +121,19 @@ static void drm_minor_alloc_release(struct drm_device *dev, void *data)
>   	xa_erase(drm_minor_get_xa(minor->type), minor->index);
>   }
>   
> +/*
> + * DRM used to support 64 devices, for backwards compatibility we need to maintain the
> + * minor allocation scheme where minors 0-63 are primary nodes, 64-127 are control nodes,
> + * and 128-191 are render nodes.
> + * After reaching the limit, we're allocating minors dynamically - first-come, first-serve.
> + * Accel nodes are using a distinct major, so the minors are allocated in continuous 0-MAX
> + * range.
> + */
>   #define DRM_MINOR_LIMIT(t) ({ \
>   	typeof(t) _t = (t); \
>   	_t == DRM_MINOR_ACCEL ? XA_LIMIT(0, ACCEL_MAX_MINORS) : XA_LIMIT(64 * _t, 64 * _t + 63); \
>   })
> +#define DRM_EXTENDED_MINOR_LIMIT XA_LIMIT(192, (1 << MINORBITS) - 1)
>   
>   static int drm_minor_alloc(struct drm_device *dev, enum drm_minor_type type)
>   {
> @@ -140,6 +149,9 @@ static int drm_minor_alloc(struct drm_device *dev, enum drm_minor_type type)
>   
>   	r = xa_alloc(drm_minor_get_xa(type), &minor->index,
>   		     NULL, DRM_MINOR_LIMIT(type), GFP_KERNEL);
> +	if (r == -EBUSY && (type == DRM_MINOR_PRIMARY || type == DRM_MINOR_RENDER))
> +		r = xa_alloc(&drm_minors_xa, &minor->index,
> +			     NULL, DRM_EXTENDED_MINOR_LIMIT, GFP_KERNEL);
>   	if (r < 0)
>   		return r;
>   
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