Re: [PATCH v3 1/7] rust: firmware: add request_into_buf()

["Alexandre Courbot" <acourbot@nvidia.com>]

On Tue Jul 7, 2026 at 11:54 AM JST, Timur Tabi wrote:
> On Mon, 2026-07-06 at 12:50 +0200, Danilo Krummrich wrote:
>> On Mon Jul 6, 2026 at 8:30 AM CEST, Alexandre Courbot wrote:
>> > Sashiko is correct to point out that this doesn't return the number of
>> > bytes actually written into `buf`. We might not use that information in
>> > nova-core, but this is a kernel-wide API.
>> 
>> Returning the size only doesn't carry a lot of value, please see [1].
>> 
>> > Returning a `Result<&[u8]>` would take care of this and cover the
>> > general use-case nicely.
>> 
>> I'm fine with either this or just Result, as we don't have a user for the
>> former.
>> 
>> [1] https://lore.kernel.org/nova-gpu/DJ6JV2QQY0QD.1ZK1PRRBN5BRP@kernel.org/
>
> Guys, please come to a consensus.  I had it return a size originally, but then Danilo said don't
> bother, and now Alex says I should return a size.

Incorrect; I said you should return a slice. :)

What makes me a bit nervous with this API is that it is not sound
against incorrect size information or race conditions (e.g. if the file
on disk changes after we determined its size). But that's true of my
proposal as well anyway.

Another inefficiency is that the buffer must be initialized when passed,
only for its content to be immediately overwritten. I'd like to make
this function accept a `MaybeUninit`, but that will require more generic
code.

All that to say, I will likely think some more about it and revisit
after it lands, but the current version does the job, so:

Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>