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    SubjectRe: [PATCH 1/2] regmap: Support half writes and padding between register and value.
    On Thu, Sep 08, 2011 at 03:09:23PM +0100, Jonathan Cameron wrote:

    > Note half writes currently assume address numbers are even only.
    > That's a pain for caching so other suggestions welcome. I could set
    > it as a 7 bit address and increase the padding to 9 bits. That makes
    > the write bit a little strange though as it will be going into the
    > padding.

    This needs more documentation somewhere explaining what a half write is
    and/or a better name for half write but doesn't look too invasive so I
    think this approach can work. If we come up with something better later
    then we can always change things, there shouldn't be too many users to
    update if that happens.

    > - map->format.reg_bytes = config->reg_bits / 8;
    > + map->format.buf_size = (config->reg_bits +
    > + config->reg_pad_bits +
    > + config->val_bits) / 8;
    > + map->format.reg_bytes = (config->reg_bits + config->reg_pad_bits)/ 8;

    Please do a patch adding padding separately - that does seem like a
    useful thing to have in general, with the option of having it both
    before and after the register.

    > - if (val == map->work_buf + map->format.reg_bytes)
    > - ret = map->bus->write(map->dev, map->work_buf,
    > - map->format.reg_bytes + val_len);
    > - else if (map->bus->gather_write)
    > + if (val == map->work_buf + map->format.reg_bytes) {
    > + if (map->format.half_write) {
    > + ret = map->bus->write(map->dev, map->work_buf,
    > + (map->format.reg_bytes +
    > + val_len) >> 1);
    > + if (ret >= 0)
    > + ret = map->bus->write(map->dev,
    > + map->work_buf +
    > + ((map->format.reg_bytes +
    > + val_len) >> 1),
    > + (map->format.reg_bytes +
    > + val_len) >> 1);
    > + } else {
    > + ret = map->bus->write(map->dev, map->work_buf,
    > + map->format.reg_bytes + val_len);
    > + }

    This code is getting very complicated... I think it'd be clearer to
    have a special case at the head of the function that does the half write
    stuff. It also feels like the half bit needs parameterisation, but I
    can't immediately think of how to do that sensibly.


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