[bug report] drm/xe/psmi: Add debugfs interface for PSMI

[Dan Carpenter <dan.carpenter@linaro.org>]

Hello Lucas De Marchi,

Commit aaa0c1f50a3d ("drm/xe/psmi: Add debugfs interface for PSMI")
from Aug 21, 2025 (linux-next), leads to the following Smatch static
checker warning:

	drivers/gpu/drm/xe/xe_psmi.c:93 psmi_alloc_object()
	error: 'bo' dereferencing possible ERR_PTR()

drivers/gpu/drm/xe/xe_psmi.c
    68 static struct xe_bo *psmi_alloc_object(struct xe_device *xe,
    69                                        unsigned int id, size_t bo_size)
    70 {
    71         struct xe_bo *bo = NULL;
    72         struct xe_tile *tile;
    73         int err;
    74 
    75         if (!id || !bo_size)
    76                 return NULL;

I really encourage everyone to document why functions return both error
pointers and NULL.  Here "bo_size" can never actually be zero so that's
an impossible path.  Presumably id can be zero, but what's the point of
storing a NULL in xe->psmi.capture_obj[0]?  It feels like it complicates
things...

    77 
    78         tile = &xe->tiles[id - 1];
    79 
    80         /* VRAM: Allocate GEM object for the capture buffer */
    81         bo = xe_bo_create_locked(xe, tile, NULL, bo_size,
    82                                  ttm_bo_type_kernel,
    83                                  XE_BO_FLAG_VRAM_IF_DGFX(tile) |
    84                                  XE_BO_FLAG_PINNED |
    85                                  XE_BO_FLAG_PINNED_LATE_RESTORE |
    86                                  XE_BO_FLAG_NEEDS_CPU_ACCESS);
    87 
    88         if (!IS_ERR(bo)) {
                   ^^^^^^^^^^
Better to flip these around.  Always do error handling, never success
handling.

    89                 /* Buffer written by HW, ensure stays resident */
    90                 err = xe_bo_pin(bo);
    91                 if (err)
    92                         bo = ERR_PTR(err);
                               ^^^^^^^^^^^^^^^^^
bo set to error pointer.

--> 93                 xe_bo_unlock(bo);
                                    ^^
Dead.

Don't we need to call xe_bo_put() or something to free the bo before
returning?  Something like this?

	if (IS_ERR(bo))
		return ERR_CAST(bo);

	/* Buffer written by HW, ensure stays resident */
	err = xe_bo_pin(bo);
	xe_bo_unlock(bo);
	if (err) {
		xe_bo_put(bo);
		return ERR_PTR(err);
	}

	return bo;

    94         }
    95 
    96         return bo;
    97 }

regards,
dan carpenter