drm: Help unconfuse gcc, avoid accidental impossible unsigned comparisons

drivers/gpu/drm/drm_client_modeset.c: In function ‘drm_client_firmware_config’:
./include/linux/bits.h:26:28: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits]
   __builtin_constant_p((l) > (h)), (l) > (h), 0)))

v2: Add a warning for passing connector_count==0 as this will hit an
infinite loop, so document the invalid parameter.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200516212330.13633-2-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/drm_client_modeset.c b/drivers/gpu/drm/drm_client_modeset.c
index 7443114..66e785b 100644 (file)
--- a/drivers/gpu/drm/drm_client_modeset.c
+++ b/drivers/gpu/drm/drm_client_modeset.c
@@ -563,7 +563,7 @@ static bool drm_client_firmware_config(struct drm_client_dev *client,
                                       struct drm_client_offset *offsets,
                                       bool *enabled, int width, int height)
 {
-       unsigned int count = min_t(unsigned int, connector_count, BITS_PER_LONG);
+       const int count = min_t(unsigned int, connector_count, BITS_PER_LONG);
        unsigned long conn_configured, conn_seq, mask;
        struct drm_device *dev = client->dev;
        int i, j;
@@ -577,6 +577,9 @@ static bool drm_client_firmware_config(struct drm_client_dev *client,
        if (!drm_drv_uses_atomic_modeset(dev))
                return false;
 
+       if (WARN_ON(count <= 0))
+               return false;
+
        save_enabled = kcalloc(count, sizeof(bool), GFP_KERNEL);
        if (!save_enabled)
                return false;