[PATCH v2 1/2] drm: Expand max DRM device number to full MINORBITS

[Michał Winiarski]

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.
This is continued for minors >= 192 (192-255 for primary, 256-319
reserved, 320-383 for render, and so on).

Signed-off-by: Michał Winiarski <michal.winiar...@intel.com>
---
 drivers/gpu/drm/drm_drv.c | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 8214a0b1ab7f..b64b5c45cd80 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -113,7 +113,7 @@ static int drm_minor_alloc(struct drm_device *dev, unsigned 
int type)
 {
        struct drm_minor *minor;
        unsigned long flags;
-       int r;
+       int r, start, end;
 
        minor = drmm_kzalloc(dev, sizeof(*minor), GFP_KERNEL);
        if (!minor)
@@ -122,15 +122,19 @@ static int drm_minor_alloc(struct drm_device *dev, 
unsigned int type)
        minor->type = type;
        minor->dev = dev;
 
-       idr_preload(GFP_KERNEL);
-       spin_lock_irqsave(&drm_minor_lock, flags);
-       r = idr_alloc(&drm_minors_idr,
-                     NULL,
-                     64 * type,
-                     64 * (type + 1),
-                     GFP_NOWAIT);
-       spin_unlock_irqrestore(&drm_minor_lock, flags);
-       idr_preload_end();
+       start = 64 * type;
+       end = 64 * (type + 1);
+
+       do {
+               idr_preload(GFP_KERNEL);
+               spin_lock_irqsave(&drm_minor_lock, flags);
+               r = idr_alloc(&drm_minors_idr, NULL, start, end, GFP_NOWAIT);
+               spin_unlock_irqrestore(&drm_minor_lock, flags);
+               idr_preload_end();
+
+               start += 192;
+               end += 192;
+       } while ((r == -ENOSPC) && end <= (1 << MINORBITS));
 
        if (r < 0)
                return r;
-- 
2.37.2