On 2/4/26 8:11 PM, John Hubbard wrote:
> The auxiliary device registration was using a hardcoded ID of 0, which
> caused probe() to fail on multi-GPU systems with:
>
> sysfs: cannot create duplicate filename
> '/bus/auxiliary/devices/NovaCore.nova-drm.0'
>
> Fix this by using an atomic counter to generate unique IDs for each
> GPU's aux device registration. The TODO item to eventually use XArray
> for recycling aux device IDs is retained, but for now, this works very
> nicely.
>
> This has the side effect of making debugfs[1] work on multi-GPU systems.
>
> [1] https://lore.kernel.org/[email protected]
>
> Signed-off-by: John Hubbard <[email protected]>
> ---
> drivers/gpu/nova-core/driver.rs | 12 +++++++++++-
> 1 file changed, 11 insertions(+), 1 deletion(-)
>
> Hi,
>
> This is based on today's (Feb 4, 2026) linux-next/master branch.
>
> thanks,
> John Hubbard
>
> diff --git a/drivers/gpu/nova-core/driver.rs b/drivers/gpu/nova-core/driver.rs
> index 5a4cc047bcfc..a542ec0b40fa 100644
> --- a/drivers/gpu/nova-core/driver.rs
> +++ b/drivers/gpu/nova-core/driver.rs
> @@ -1,5 +1,7 @@
> // SPDX-License-Identifier: GPL-2.0
>
> +use core::sync::atomic::{AtomicU32, Ordering};
Somehow the wrong (non-vertical) formatting snuck back into
my patch! Arggh. I'll be glad when rustfmt support for this
can help me catch this.
> +
> use kernel::{
> auxiliary,
> device::Core,
> @@ -19,6 +21,9 @@
>
> use crate::gpu::Gpu;
>
> +/// Counter for generating unique auxiliary device IDs.
> +static AUXILIARY_ID_COUNTER: AtomicU32 = AtomicU32::new(0);
> +
> #[pin_data]
> pub(crate) struct NovaCore {
> #[pin]
> @@ -85,12 +90,17 @@ fn probe(pdev: &pci::Device<Core>, _info: &Self::IdInfo)
> -> impl PinInit<Self, E
> GFP_KERNEL,
> )?;
>
> + // TODO[XARR]: Use XArray for proper ID allocation/recycling;
> for now we use a simple
I also did *not* mean to leave the word "we" in there.
Lots of little glitches tonight, sorry about those.
thanks,
--
John Hubbard
> + // atomic counter which never recycles IDs. A unique ID is
> required for multi-GPU
> + // systems; without it, probe() fails for all but the first GPU.
> + let aux_id = AUXILIARY_ID_COUNTER.fetch_add(1,
> Ordering::Relaxed);
> +
> Ok(try_pin_init!(Self {
> gpu <- Gpu::new(pdev, bar.clone(),
> bar.access(pdev.as_ref())?),
> _reg <- auxiliary::Registration::new(
> pdev.as_ref(),
> c"nova-drm",
> - 0, // TODO[XARR]: Once it lands, use XArray; for now we
> don't use the ID.
> + aux_id,
> crate::MODULE_NAME
> ),
> }))
>
> base-commit: 0f8a890c4524d6e4013ff225e70de2aed7e6d726
