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Date:   Tue, 11 Apr 2023 22:58:34 -0400
From:   "Theodore Ts'o" <tytso@mit.edu>
To:     Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Cc:     Deborah Brouwer <deborah.brouwer@collabora.com>,
        Daniel Almeida <daniel.almeida@collabora.com>,
        wedsonaf@gmail.com, ojeda@kernel.org, mchehab@kernel.org,
        hverkuil@xs4all.nl, rust-for-linux@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-media@vger.kernel.org,
        kernel@collabora.com
Subject: Re: [PATCH 0/6] Initial Rust V4L2 support
Message-ID: <20230412025834.GA301301@mit.edu>
References: <20230406215615.122099-1-daniel.almeida@collabora.com>
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 <CANiq72=n1b=fJ2XZZx_MLKkbKMTmnmTBMgA3GJ_hqyARPtwEiQ@mail.gmail.com>
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On Tue, Apr 11, 2023 at 04:22:56PM +0200, Miguel Ojeda wrote:
> 
> Thanks, it is great to hear that the guide helped! :)
> 
> On resources: nowadays we have a webpage, too. Still to be completed,
> but you may find it useful already: https://rust-for-linux.com

Something that would perhaps be useful is to document (a) what
versions of Rust is available for various distributions, or pointers
to how to get that information for various distributions.  For
example, you can get that information from Debian using [1].  It
appears that Fedora isn't distributing rustc at *all*, at least
according to [2], so apparently for Fedora people will need to install
it from source.

[1] https://packages.debian.org/search?keywords=rustc&searchon=names&suite=all&section=all
[2] https://idroot.us/install-rust-fedora-37/

The other thing that would be worth documenting is (b) something about
what versions of Rust people have actually tested.  The comments at
[3] are quite scary, since per [4], the minimum version of Rustc
supported is 1.62.0 --- and per [3], **only** Rust 1.62.0 is
supported, since we use unstable Rust features.

[3] https://rust-for-linux.com/rust-version-policy
[4] https://docs.kernel.org/process/changes.html

But for example, with Debian, Debian stable is shipping Rust 1.48.0,
and Debian testing (which is currently in "hard freeze" so it can be
released as Debian stable this summer) is shipping Rustc 1.63.0.

Since I use Debian testing, the question which is foremost in my mind
is whether I can expect to have things work if I use the
distro-provided 1.63.0 rustc, or is this really a case of "it's not
Rust 1.62.0, so good luck to you"?

If the goal is accelerate adoption of Rustc, and calm people's fears
vis-a-vis using Rust, it's not enough to say, "why don't you use the
distribution-provided version or Rust"?  It would be helpful if those
Rust pioneers can share what versions of Rust they have tested
against, especially for those commonly used distributions, such as
Debian, and give us a report whether we should expect things to work,
so we can ignore the scary warning from the build system that we're
using an unsupported version of Rust, and if it breaks, we get to keep
both pieces.

And for those distributions that don't currently ship Rust, such as
Fedora, if someone could build their own unofficial packages, until we
can convince Red Hat to start shipping -their own supported Rust
compilers, that might be a great way of bridging that gap.

Cheers,

					- Ted