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    SubjectRe: [PATCH 03/14 v3] Input: atmel_mxt_ts - refactor mxt_read/write_reg to take a length
    On Wed, May 09, 2012 at 09:05:00AM +0200, Jean Delvare wrote:
    > Hi Dmirty,
    >
    > On Tue, 8 May 2012 22:54:11 -0700, Dmitry Torokhov wrote:
    > > Hi Daniel,
    > >
    > > On Wed, Apr 18, 2012 at 09:21:48PM +0800, Daniel Kurtz wrote:
    > > > + ret = i2c_transfer(client->adapter, xfer, 2);
    > > > + if (ret != 2) {
    > > > + dev_err(&client->dev, "i2c read reg failed (%d)\n", ret);
    > > > + if (ret >= 0)
    > > > + ret = -EIO;
    > > > }
    > > >
    > > > - return 0;
    > > > + return (ret == 2) ? 0 : ret;
    > > > }
    > >
    > > Would prefer:
    > >
    > > ret = i2c_transfer(client->adapter, xfer, ARRAY_SIZE(xfer));
    > > if (ret != ARRAY_SIZE(xfer)) {
    > > if (ret >= 0)
    > > ret = -EIO;
    > > dev_err(&client->dev, "i2c read reg failed (%d)\n", ret);
    > > return ret;
    > > }
    > >
    > > return 0;
    > >
    > >
    > > Or maybe we need i2c_transfer_exact() wrapper? Jean?
    >
    > What would this function do? Return 0 on success instead of the number
    > of transferred messages? And -EIO on partial transfers?

    Yes, exactly.

    >
    > That would make sense. Partial success is a rare case anyway, and
    > recovery possibilities are even rarer. I think most drivers don't
    > bother and either retry the whole transaction or fail right away. In
    > fact the number of messages successfully transferred is more useful to
    > diagnose problems during driver development or debugging.
    >
    > Feel free to write and send a patch introducing i2c_transfer_exact().
    > It would make sense to have it log a debug message on partial success,
    > as it is a rare case. Bonus points if you also sent one or more patches
    > converting (some of) the existing callers to make use of the new
    > function.

    OK, thanks.

    --
    Dmitry


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