[PATCH v6 09/11] drm/xe/configfs: Check if device was preconfigured

[Lucas De Marchi]

On Thu, Jul 31, 2025 at 09:33:37PM +0200, Michal Wajdeczko wrote:
>Since device configuration using configfs could be prepared long
>time prior the driver load, add a debug log whether the current
>device driver probe is using custom or default settings.
>
>Signed-off-by: Michal Wajdeczko <michal.wajdeczko at intel.com>
>Cc: Lucas De Marchi <lucas.demarchi at intel.com>
>Reviewed-by: John Harrison <John.C.Harrison at Intel.com>
>---
>v2: make function void, rename helpers (Lucas) and rebased
>---
> drivers/gpu/drm/xe/xe_configfs.c | 25 +++++++++++++++++++++++++
> drivers/gpu/drm/xe/xe_configfs.h |  2 ++
> drivers/gpu/drm/xe/xe_pci.c      |  3 +++
> 3 files changed, 30 insertions(+)
>
>diff --git a/drivers/gpu/drm/xe/xe_configfs.c b/drivers/gpu/drm/xe/xe_configfs.c
>index 150e7f2becc8..5f145ccdf535 100644
>--- a/drivers/gpu/drm/xe/xe_configfs.c
>+++ b/drivers/gpu/drm/xe/xe_configfs.c
>@@ -107,6 +107,11 @@ static void set_device_defaults(struct xe_config_device *config)
> 	*config = device_defaults;
> }
>
>+static bool config_device_is_default(const struct xe_config_device *config)

this isn't exactly safe and as such shouldn't be a helper that can be
misused.

$ pahole -C xe_config_device /p2/build-drm-xe-next/drivers/gpu/drm/xe/xe.o
struct xe_config_device {
         bool                       survivability_mode;   /*     0     1 */

         /* XXX 7 bytes hole, try to pack */

         u64                        engines_allowed;      /*     8     8 */

         /* size: 16, cachelines: 1, members: 2 */
         /* sum members: 9, holes: 1, sum holes: 7 */
         /* last cacheline: 16 bytes */
};

>+{
>+	return !memcmp(config, &device_defaults, sizeof(*config));
>+}
>+
> struct engine_info {
> 	const char *cls;
> 	u64 mask;
>@@ -339,6 +344,26 @@ static struct xe_config_group_device *find_xe_config_group_device(struct pci_dev
> 	return to_xe_config_group_device(item);
> }
>
>+/**
>+ * xe_configfs_check_device() - Test if device was configured by configfs
>+ * @pdev: the &pci_dev device to test
>+ *
>+ * Try to find the configfs group that belongs to the specified pci device
>+ * and print a diagnostic message if found.
>+ */
>+void xe_configfs_check_device(struct pci_dev *pdev)
>+{
>+	struct xe_config_group_device *dev = find_xe_config_group_device(pdev);
>+
>+	if (!dev)
>+		return;
>+
>+	pci_dbg(pdev, "found %s settings in configfs\n",
>+		config_device_is_default(&dev->config) ? "default" : "custom");

I guess comparing dev->config and device_defaults is safe because both
will zero-initialize the hole (or padding if we had one): the former is
allocated via kzalloc() and the latter has static storage.

I'd just remove the helper and do the memcmp explicitly in this
function.

Lucas De Marchi

>+
>+	config_group_put(&dev->group);
>+}
>+
> /**
>  * xe_configfs_get_survivability_mode - get configfs survivability mode attribute
>  * @pdev: pci device
>diff --git a/drivers/gpu/drm/xe/xe_configfs.h b/drivers/gpu/drm/xe/xe_configfs.h
>index fb8764008089..fa4ea7f0c375 100644
>--- a/drivers/gpu/drm/xe/xe_configfs.h
>+++ b/drivers/gpu/drm/xe/xe_configfs.h
>@@ -13,12 +13,14 @@ struct pci_dev;
> #if IS_ENABLED(CONFIG_CONFIGFS_FS)
> int xe_configfs_init(void);
> void xe_configfs_exit(void);
>+void xe_configfs_check_device(struct pci_dev *pdev);
> bool xe_configfs_get_survivability_mode(struct pci_dev *pdev);
> void xe_configfs_clear_survivability_mode(struct pci_dev *pdev);
> u64 xe_configfs_get_engines_allowed(struct pci_dev *pdev);
> #else
> static inline int xe_configfs_init(void) { return 0; }
> static inline void xe_configfs_exit(void) { }
>+static inline void xe_configfs_check_device(struct pci_dev *pdev) { }
> static inline bool xe_configfs_get_survivability_mode(struct pci_dev *pdev) { return false; }
> static inline void xe_configfs_clear_survivability_mode(struct pci_dev *pdev) { }
> static inline u64 xe_configfs_get_engines_allowed(struct pci_dev *pdev) { return U64_MAX; }
>diff --git a/drivers/gpu/drm/xe/xe_pci.c b/drivers/gpu/drm/xe/xe_pci.c
>index 52d46c66ae1e..9ce6e6dca5bc 100644
>--- a/drivers/gpu/drm/xe/xe_pci.c
>+++ b/drivers/gpu/drm/xe/xe_pci.c
>@@ -17,6 +17,7 @@
>
> #include "display/xe_display.h"
> #include "regs/xe_gt_regs.h"
>+#include "xe_configfs.h"
> #include "xe_device.h"
> #include "xe_drv.h"
> #include "xe_gt.h"
>@@ -771,6 +772,8 @@ static int xe_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
> 	struct xe_device *xe;
> 	int err;
>
>+	xe_configfs_check_device(pdev);
>+
> 	if (desc->require_force_probe && !id_forced(pdev->device)) {
> 		dev_info(&pdev->dev,
> 			 "Your graphics device %04x is not officially supported\n"
>-- 
>2.47.1
>