On Sat Oct 25, 2025 at 2:14 AM CEST, John Hubbard wrote:
> + // "next-gen" GPUs (some time after Blackwell) will zero out boot0,
> and put the architecture
> + // details in boot42 instead. Avoid reading boot42 unless we are in
> that case.
> + let boot42 = if boot0.is_next_gen() {
> + Some(regs::NV_PMC_BOOT_42::read(bar))
> + } else {
> + None
> + };
> +
> try_pin_init!(Self {
> chipset: {
> - let chipset = boot0.chipset()?;
> + // Some brief notes about boot0 and boot42, in chronological
> order:
> + //
> + // NV04 through Volta:
> + //
> + // Not supported by Nova. boot0 is necessary and
> sufficient to identify these
> + // GPUs. boot42 may not even exist on some of these GPUs.
> + //
> + // Turing through Blackwell:
> + //
> + // Supported by both Nouveau and Nova. boot0 is still
> necessary and sufficient
> + // to identify these GPUs. boot42 exists on these GPUs
> but we don't need to use
> + // it.
> + //
> + // Future "next-gen" GPUs:
> + //
> + // Only supported by Nova. Boot42 has the architecture
> details, boot0 is zeroed
> + // out.
> +
> + // NV04, the very first NVIDIA GPU to be supported on Linux,
> is identified by a
> + // specific bit pattern in boot0. Although Nova does not
> support NV04 (see above),
> + // it is possible to confuse NV04 with a "next-gen" GPU.
> Therefore, return early if
> + // we specifically detect NV04, thus simplifying the
> remaining selection logic.
> + if boot0.is_nv04() {
> + Err(ENODEV)?
> + }
> +
> + // Now that we know it is something more recent than NV04,
> use boot42 if we
> + // previously determined that boot42 was both valid and
> relevant, and boot0
> + // otherwise.
> + let (chipset, major_rev, minor_rev) = if let Some(boot42) =
> boot42 {
> + (
> + boot42.chipset()?,
> + boot42.major_revision(),
> + boot42.minor_revision(),
> + )
> + } else {
> + // Current/older GPU: use BOOT0
> + (
> + boot0.chipset()?,
> + boot0.major_revision(),
> + boot0.minor_revision(),
> + )
> + };
Why open code all of the above in the struct Gpu constructor? This could all
happen within Spec::new().
If we *really* don't want to store the Spec, but only the Chipset, you can also
do:
try_pin_init!(Self {
chipset: {
let spec = Spec::new(bar);
dev_info!(pdev.as_ref(), "{}\n", spec);
spec.chipset
},
[...],
}
