Re: [PATCH 0/6] rust: drm: Higher-Ranked Lifetime private data

["Danilo Krummrich" <dakr@kernel.org>]

On Thu May 7, 2026 at 12:05 AM CEST, Danilo Krummrich wrote:
> Danilo Krummrich (6):
>   rust: drm: Add Driver::ParentDevice associated type
>   rust: drm: Add UnbindGuard for drm_dev_enter/exit critical sections
>   rust: drm: Add RegistrationData to drm::Driver
>   rust: drm: Wrap ioctl dispatch in UnbindGuard
>   rust: drm: Pass registration data to ioctl handlers
>   rust: drm: Pass bound parent device to ioctl handlers

Deborah, following up on your question in the other thread, this is roughly how
you'd use this in Tyr.

diff --git a/drivers/gpu/drm/tyr/driver.rs b/drivers/gpu/drm/tyr/driver.rs
index 7ac3707823b6..447e53c0eecf 100644
--- a/drivers/gpu/drm/tyr/driver.rs
+++ b/drivers/gpu/drm/tyr/driver.rs
@@ -37,13 +37,17 @@
     regs, //
 };

-pub(crate) type IoMem = kernel::io::Mmio<SZ_2M>;
+pub(crate) type IoMem<'bound> = kernel::io::mem::IoMem<'bound, SZ_2M>;

 pub(crate) struct TyrDrmDriver;

 /// Convenience type alias for the DRM device type for this driver.
 pub(crate) type TyrDrmDevice<Ctx = drm::Registered> = drm::Device<TyrDrmDriver, Ctx>;

+pub(crate) struct RegData<'bound> {
+    pub(crate) iomem: IoMem<'bound>,
+}
+
 #[pin_data(PinnedDrop)]
 pub(crate) struct TyrPlatformDriverData {
     _device: ARef<TyrDrmDevice>,
@@ -65,7 +69,7 @@ pub(crate) struct TyrDrmDeviceData {
     pub(crate) gpu_info: GpuInfo,
 }

-fn issue_soft_reset(dev: &Device<Bound>, iomem: &IoMem) -> Result {
+fn issue_soft_reset(dev: &Device<Bound>, iomem: &IoMem<'_>) -> Result {
     regs::GPU_CMD.write(iomem, regs::GPU_CMD_SOFT_RESET);

     poll::read_poll_timeout(
@@ -133,8 +137,10 @@ fn probe(
                 gpu_info,
         });

+        let reg_data = RegData { iomem };
+
         let tdev = drm::UnregisteredDevice::<TyrDrmDriver>::new(pdev, data)?;
-        let tdev = drm::driver::Registration::new_foreign_owned(tdev, pdev.as_ref(), (), 0)?;
+        let tdev = drm::driver::Registration::new_foreign_owned(tdev, pdev.as_ref(), reg_data, 0)?;

         let driver = TyrPlatformDriverData {
             _device: tdev.into(),
@@ -176,7 +182,7 @@ fn drop(self: Pin<&mut Self>) {
 #[vtable]
 impl drm::Driver for TyrDrmDriver {
     type Data = TyrDrmDeviceData;
-    type RegistrationData = ForLt!(());
+    type RegistrationData = ForLt!(for<'a> RegData<'a>);
     type File = TyrDrmFileData;
     type Object<R: drm::DeviceContext> = drm::gem::Object<TyrObject, R>;
     type ParentDevice<Ctx: DeviceContext> = platform::Device<Ctx>;
diff --git a/drivers/gpu/drm/tyr/file.rs b/drivers/gpu/drm/tyr/file.rs
index 9f53da7633ab..30efdf924cc2 100644
--- a/drivers/gpu/drm/tyr/file.rs
+++ b/drivers/gpu/drm/tyr/file.rs
@@ -10,6 +10,7 @@
 };

 use crate::driver::{
+    RegData,
     TyrDrmDevice,
     TyrDrmDriver, //
 };
@@ -32,10 +33,12 @@ impl TyrDrmFileData {
     pub(crate) fn dev_query(
         ddev: &TyrDrmDevice,
         _pdev: &platform::Device<device::Bound>,
-        _reg_data: &(),
+        reg_data: &RegData<'_>,
         devquery: &mut uapi::drm_panthor_dev_query,
         _file: &TyrDrmFile,
     ) -> Result<u32> {
+        let _iomem = reg_data.iomem;
+
         if devquery.pointer == 0 {
             match devquery.type_ {
                 uapi::drm_panthor_dev_query_type_DRM_PANTHOR_DEV_QUERY_GPU_INFO => {
diff --git a/drivers/gpu/drm/tyr/gpu.rs b/drivers/gpu/drm/tyr/gpu.rs
index bb0473c85bf7..f169fb1ccc03 100644
--- a/drivers/gpu/drm/tyr/gpu.rs
+++ b/drivers/gpu/drm/tyr/gpu.rs
@@ -34,7 +34,7 @@
 pub(crate) struct GpuInfo(pub(crate) uapi::drm_panthor_gpu_info);

 impl GpuInfo {
-    pub(crate) fn new(iomem: &IoMem) -> Self {
+    pub(crate) fn new(iomem: &IoMem<'_>) -> Self {
         let gpu_id = regs::GPU_ID.read(iomem);
         let csf_id = regs::GPU_CSF_ID.read(iomem);
         let gpu_rev = regs::GPU_REVID.read(iomem);
@@ -206,7 +206,7 @@ fn from(value: u32) -> Self {
 }

 /// Powers on the l2 block.
-pub(crate) fn l2_power_on(dev: &Device<Bound>, iomem: &IoMem) -> Result {
+pub(crate) fn l2_power_on(dev: &Device<Bound>, iomem: &IoMem<'_>) -> Result {
     regs::L2_PWRON_LO.write(iomem, 1);

     poll::read_poll_timeout(
diff --git a/drivers/gpu/drm/tyr/regs.rs b/drivers/gpu/drm/tyr/regs.rs
index 0881b3812afd..2b0da6019512 100644
--- a/drivers/gpu/drm/tyr/regs.rs
+++ b/drivers/gpu/drm/tyr/regs.rs
@@ -20,12 +20,12 @@

 impl<const OFFSET: usize> Register<OFFSET> {
     #[inline]
-    pub(crate) fn read(&self, iomem: &IoMem) -> u32 {
+    pub(crate) fn read(&self, iomem: &IoMem<'_>) -> u32 {
         iomem.read32(OFFSET)
     }

     #[inline]
-    pub(crate) fn write(&self, iomem: &IoMem, value: u32) {
+    pub(crate) fn write(&self, iomem: &IoMem<'_>, value: u32) {
         iomem.write32(value, OFFSET);
     }
 }