On Wed, 31 Aug 2022 15:40:49 +0300
Andy Shevchenko <andy.shevchenko@xxxxxxxxx> wrote:
> On Wed, Aug 31, 2022 at 1:05 PM Vincent Whitchurch
> <vincent.whitchurch@xxxxxxxx> wrote:
> >
> > Replace the device_index switch with callbacks from the chip_info
> > structure, so that the latter has all the information needed to handle
> > the variants.
>
> Below are for the further patches, as I see the original code has the
> same disadvantages.
>
> ...
>
> > struct mcp320x_chip_info {
> > const struct iio_chan_spec *channels;
> > unsigned int num_channels;
> > unsigned int resolution;
>
> > unsigned int conv_time; /* usec */
>
> Instead of a comment, I would rename it to conv_time_us.
>
> > + int (*convert_rx)(struct mcp320x *adc);
> > };
>
> ...
>
> > + return adc->rx_buf[0] << 5 | adc->rx_buf[1] >> 3;
>
> > + return adc->rx_buf[0] << 2 | adc->rx_buf[1] >> 6;
>
> > + return adc->rx_buf[0] << 7 | adc->rx_buf[1] >> 1;
>
> > + return adc->rx_buf[0] << 4 | adc->rx_buf[1] >> 4;
>
> > + return sign_extend32((adc->rx_buf[0] & 0x1f) << 8 | adc->rx_buf[1], 12);
>
> All above should really use
>
> u16 buf = be16_to_cpu(&adc->rx_buf[0]);
>
> return buf >> 3 /* 6, 1, 4 (respectively) */;
This made me look a bit closer at the code.
rx_buf isn't necessarily aligned...
This may be a good usecase for an anonymous union.
Which would be fine except one of the callbacks (and original
code) uses be32_to_cpup() which is not unaligned safe.
I'm not keen to push unrelated work onto someone doing good stuff
on a driver, but in this particular case it does seem reasonable to
tidy all this up given you are moving the code anyway.
Jonathan
>
> ...
>
> > + if (raw & BIT(22) && raw & BIT(23))
>
> > + return -EIO; /* cannot have overrange AND underrange */
> > + else if (raw & BIT(22))
>
> Redundant 'else'.
>
> > + raw &= ~BIT(22); /* overrange */
> > + else if (raw & BIT(23) || raw & BIT(21))
>
> if (raw & (BIT(23) | BIT(21))) ?
>
> > + raw |= GENMASK(31, 22); /* underrange or negative */
>
> ...
>
> > [mcp3201] = {
> > .channels = mcp3201_channels,
> > .num_channels = ARRAY_SIZE(mcp3201_channels),
> > + .convert_rx = mcp3201_convert_rx,
>
> > .resolution = 12
>
> + Comma in such lines.
>
> > },
>
