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    SubjectRe: [PATCH v10] i2c: virtio: add a virtio i2c frontend driver
    I will be replying here instead of replying to each and every msg :)

    On 28-06-21, 16:58, Wolfram Sang wrote:
    >
    > > You can fine Viresh's vhost-user implementation at
    > > https://lore.kernel.org/qemu-devel/cover.1617278395.git.viresh.kumar@linaro.org/t/#m3b5044bad9769b170f505e63bd081eb27cef8db2
    >
    > It looks OK so far; yet, it is not complete. But it might be bearable
    > in the end.

    While we are at it, this has been replaced by a Rust counterpart [1]
    (as that makes it hypervisor agnostic, which is the goal of my work
    here) and I need someone with I2C knowledge to help review it. It
    should be okay even if you don't understand Rust a lot, just review
    this file[2] which is where most of i2c specific stuff lies.

    > > As you say, it does get a bit clumsy, but I think there is also a good argument
    > > to be made that the clumsiness is based on the host Linux user interface
    > > more than the on the requirements of the physical interface,
    > > and that should not have to be reflected in the virtio specification.
    >
    > Makes sense to me.
    >
    > > Right, this one has come up before as well: the preliminary result
    > > was to assume that this probably won't be needed, but would be easy
    > > enough to add later if necessary.
    >
    > If adding support incrementally works for such an interface, this makes
    > sense as well.

    Yes, we don't support few of SMBUS transaction (the block ones) as you
    specified.

    > So, where are we?

    The virtio specification is already merged and here is the latest
    version [3].

    > As I understand, this v10 does not support I2C transactions (or
    > I2C_RDWR as you said).

    I am not sure why you say I2C_RDWR isn't supported. The spec and Linux
    driver (+ my Rust/qemu backend), they all support I2C_RDWR as well as
    SMBUS. To clarify on an earlier point, every virtio transfer may
    contain one or more struct i2c_msg instances, all processed together
    (as expected).

    If you see virtio_i2c_send_reqs() in this patch, you will see that it
    converts a stream of i2c_req messages to their virtio counterparts and
    send them together, consider it a single transaction.

    > But you want to support all clients. So, this doesn't match, or?

    --
    viresh

    [1] https://github.com/rust-vmm/vhost-device/pull/1
    [2] https://github.com/rust-vmm/vhost-device/blob/5aa22c92faac84ab07b6b15a214513556e8b1d01/src/i2c/src/i2c.rs
    [3] https://github.com/oasis-tcs/virtio-spec/blob/master/virtio-i2c.tex

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