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?
>>
>> More in general, unsafe code should be the absolute last resort. If we add
>> new
>> unsafe code I'd love to see a comment justifying why there's no other way
>> than
>> using unsafe code for this, as we agreed in [2].
>>
>> I did a quick grep on this series and I see 21 occurrences of "unsafe", if I
>> substract the ones for annotations and for FromBytes impls, it's still 9 new
>> ones. :(
>>
>> Do we really need all of them?
>
> I've counted 16 uses of `unsafe`. :)
I did a grep | wc on the mbox file, so it includes the 5 additional occurrences
from the annotations. :)
Otherwise the 9 "real" ones I counted seem to match the 3 bindgen ones (fine of
course) plus the 5 ones from the pin initializers (we should avoid them).
>
> - 3 in the bindgen-generated code (these can't be avoided),
> - 7 to implement `FromBytes`,
> - 1 to work around the fact that `FromBytes` doesn't work on slices yet
> (maybe that one can be removed)
> - 5 as a result of intra-dependencies in PinInit initializers (which we
> might be able to remove if I figure out how to use `pin_chain`).
>
> So best-case scenario would be that we will be down to 10 that are truly
> unavoidable.
