On Wed Sep 3, 2025 at 5:26 PM JST, Danilo Krummrich wrote:
> On Wed Sep 3, 2025 at 9:08 AM CEST, Alexandre Courbot wrote:
>> On Wed Sep 3, 2025 at 4:53 AM JST, Danilo Krummrich wrote:
>>> On Tue Sep 2, 2025 at 4:31 PM CEST, Alexandre Courbot wrote:
>>>> diff --git a/drivers/gpu/nova-core/driver.rs
>>>> b/drivers/gpu/nova-core/driver.rs
>>>> index
>>>> 274989ea1fb4a5e3e6678a08920ddc76d2809ab2..1062014c0a488e959379f009c2e8029ffaa1e2f8
>>>> 100644
>>>> --- a/drivers/gpu/nova-core/driver.rs
>>>> +++ b/drivers/gpu/nova-core/driver.rs
>>>> @@ -6,6 +6,8 @@
>>>>
>>>> #[pin_data]
>>>> pub(crate) struct NovaCore {
>>>> + // Placeholder for the real `Gsp` object once it is built.
>>>> + pub(crate) gsp: (),
>>>> #[pin]
>>>> pub(crate) gpu: Gpu,
>>>> _reg: auxiliary::Registration,
>>>> @@ -40,8 +42,14 @@ fn probe(pdev: &pci::Device<Core>, _info:
>>>> &Self::IdInfo) -> Result<Pin<KBox<Self
>>>> )?;
>>>>
>>>> let this = KBox::pin_init(
>>>> - try_pin_init!(Self {
>>>> + try_pin_init!(&this in Self {
>>>> gpu <- Gpu::new(pdev, bar)?,
>>>> + gsp <- {
>>>> + // SAFETY: `this.gpu` is initialized to a valid value.
>>>> + let gpu = unsafe { &(*this.as_ptr()).gpu };
>>>> +
>>>> + gpu.start_gsp(pdev)?
>>>> + },
>>>
>>> Please use pin_chain() [1] for this.
>>
>> Sorry, but I couldn't figure out how I can use pin_chain here (and
>> couldn't find any relevant example in the kernel code either). Can you
>> elaborate a bit?
>
> I thought of just doing the following, which I think should be equivalent
> (diff
> against current nova-next).
>
> diff --git a/drivers/gpu/nova-core/driver.rs b/drivers/gpu/nova-core/driver.rs
> index 274989ea1fb4..6d62867f7503 100644
> --- a/drivers/gpu/nova-core/driver.rs
> +++ b/drivers/gpu/nova-core/driver.rs
> @@ -41,7 +41,9 @@ fn probe(pdev: &pci::Device<Core>, _info: &Self::IdInfo) ->
> Result<Pin<KBox<Self
>
> let this = KBox::pin_init(
> try_pin_init!(Self {
> - gpu <- Gpu::new(pdev, bar)?,
> + gpu <- Gpu::new(pdev, bar)?.pin_chain(|gpu| {
> + gpu.start_gsp(pdev)
> + }),
> _reg: auxiliary::Registration::new(
> pdev.as_ref(),
> c_str!("nova-drm"),
> diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
> index 8caecaf7dfb4..211bc1a5a5b3 100644
> --- a/drivers/gpu/nova-core/gpu.rs
> +++ b/drivers/gpu/nova-core/gpu.rs
> @@ -266,7 +266,7 @@ fn run_fwsec_frts(
> pub(crate) fn new(
> pdev: &pci::Device<device::Bound>,
> devres_bar: Arc<Devres<Bar0>>,
> - ) -> Result<impl PinInit<Self>> {
> + ) -> Result<impl PinInit<Self, Error>> {
> let bar = devres_bar.access(pdev.as_ref())?;
> let spec = Spec::new(bar)?;
> let fw = Firmware::new(pdev.as_ref(), spec.chipset,
> FIRMWARE_VERSION)?;
> @@ -302,11 +302,16 @@ pub(crate) fn new(
>
> Self::run_fwsec_frts(pdev.as_ref(), &gsp_falcon, bar, &bios,
> &fb_layout)?;
>
> - Ok(pin_init!(Self {
> + Ok(try_pin_init!(Self {
> spec,
> bar: devres_bar,
> fw,
> sysmem_flush,
> }))
> }
> +
> + pub(crate) fn start_gsp(&self, _pdev: &pci::Device<device::Core>) ->
> Result {
> + // noop
> + Ok(())
> + }
> }
>
> But maybe it doesn't capture your intend?
The issue is that `start_gsp` returns a value (currently a placeholder
`()`, but it will change into a real type) that needs to be stored into
the newly-introduced `gsp` member of `NovaCore`. I could not figure how
how `pin_chain` could help with this (and this is the same problem for
the other `unsafe` statements in `firmware/gsp.rs`).
It is a common pattern when initializing a pinned object, so I agree it
would be nice support this without unsafe code.
