turnip: Fix error handling of DRM_MSM_GEM_INFO ioctls.

drmCommandWriteRead gives us a -errno, and we only checked for -1 (-EPERM,
incidentally).  All the callers wanted 0 for errors, which they were
getting by the fact that req.value was 0-initialized in our stack
allocation (though this only works as long as the kernel doesn't return an
error after setting req.value to something), and -EPERM not really being
an answer we would expect from an ioctl at this stage in the driver.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/2769>

1 files changed, 11 insertions, 5 deletions

diff --git a/src/freedreno/vulkan/tu_drm.c b/src/freedreno/vulkan/tu_drm.c
index 5e91adaf89e..f886c875088 100644
--- a/src/freedreno/vulkan/tu_drm.c
+++ b/src/freedreno/vulkan/tu_drm.c
@@ -168,7 +168,7 @@ tu_gem_close(const struct tu_device *dev, uint32_t gem_handle)
    drmIoctl(dev->physical_device->local_fd, DRM_IOCTL_GEM_CLOSE, &req);
 }
 
-/** Return UINT64_MAX on error. */
+/** Helper for DRM_MSM_GEM_INFO, returns 0 on error. */
 static uint64_t
 tu_gem_info(const struct tu_device *dev, uint32_t gem_handle, uint32_t info)
 {
@@ -179,20 +179,26 @@ tu_gem_info(const struct tu_device *dev, uint32_t gem_handle, uint32_t info)
 
    int ret = drmCommandWriteRead(dev->physical_device->local_fd,
                                  DRM_MSM_GEM_INFO, &req, sizeof(req));
-   if (ret == -1)
-      return UINT64_MAX;
+   if (ret < 0)
+      return 0;
 
    return req.value;
 }
 
-/** Return UINT64_MAX on error. */
+/** Returns the offset for CPU-side mmap of the gem handle.
+ *
+ * Returns 0 on error (an invalid mmap offset in the DRM UBI).
+ */
 uint64_t
 tu_gem_info_offset(const struct tu_device *dev, uint32_t gem_handle)
 {
    return tu_gem_info(dev, gem_handle, MSM_INFO_GET_OFFSET);
 }
 
-/** Return UINT64_MAX on error. */
+/** Returns the the iova of the BO in GPU memory.
+ *
+ * Returns 0 on error (an invalid iova in the MSM DRM UABI).
+ */
 uint64_t
 tu_gem_info_iova(const struct tu_device *dev, uint32_t gem_handle)
 {