Some comments about one routine; presumably more to follow:
On Friday 06 June 2008, Guennadi Liakhovetski wrote:
> +/**
> + * max7301_read - Read back register content
> + * @spi: The SPI device
> + * @reg: Register offset
> + *
> + * A read from the MAX7301 means one message with two transfers
That's not what you implement though ... what it needs is:
- transfer #1:
* select
* write 16 bit command, discard rx data
* deselect
- transfer #2
* select
* write 16 bit command, saving rx data
* deselect
That's from the data sheet. Now, that *could* be implemented
with a single message ... or, as you do, with two messages.
You should at least correct the comment, if you don't want to
switch to a slightly faster single-message implementation. :)
> + *
> + * Returns positive 8 bit value from device if successfull or a
> + * negative value on error
Actually it returns a 16 bit value... also, "successful" has one "l".
You seem to have forgotten to mask off the high byte ...
> + */
> +static int max7301_read(struct spi_device *spi, unsigned int reg)
> +{
> + int ret;
> + u16 word;
> +
> + word = 0x8000 | (reg << 8);
> + if ((ret = spi_write(spi, (const u8*)&word, siz
> eof(word))) != 0)
> + return ret;
> + /*
> + * FIXME: This read should write 0x0000 (=NOOP at MAX7301 side)
Take out this FIXME, and just replace it with a note that this relies
on the fact that TX always shifts out zeroes if there's no data specified.
> + */
> + if ((ret = spi_read(spi, (u8*)&word, sizeof(word))))
> + return ret;
> + return word;
> +}
> +
Oh, and in the probe():
> + spi->master->setup(spi);
should be
ret = spi_setup(spi);
if (ret < 0)
return ret;
It's quite possible that something get misconfigured, so you end up trying
to talk through a spi_master controller that doesn't support 16-bit words.
- Dave
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