[PATCH v2] GPIO: add Microchip MCP23017 / MCP23008 GPIO driver

[Trent Piepho]

On Tue, 2015-12-15 at 18:28 +0100, Florian Vallee wrote:
> +
> +/* A given spi_device can represent up to eight mcp23sxx chips
> + * sharing the same chipselect but using different addresses
> + * (e.g. chips #0 and #3 might be populated, but not #1 or $2).
> + * Driver data holds all the per-chip data.
> + */
> +struct mcp23s08_driver_data {
> +	unsigned		ngpio;
> +	struct mcp23s08		*mcp[8];
> +	struct mcp23s08		chip[];
> +};

It doesn't look like anything uses this struct.

> +static int
> +mcp23008_read_regs(struct mcp23s08 *mcp, unsigned reg, u16 *vals, unsigned n)
> +{
> +	while (n--) {
> +		int ret = mcp23008_read(mcp, reg++);

This could use mcp->ops->read(mcp, reg++) instead of mcp23008_read().
Which would make it exactly the same as this function:

> +static int
> +mcp23017_read_regs(struct mcp23s08 *mcp, unsigned reg, u16 *vals, unsigned n)
> +{
> +	while (n--) {
> +		int ret = mcp23017_read(mcp, reg++);
> +		if (ret < 0)
> +			return ret;
> +		*vals++ = ret;
> +	}
> +
> +	return 0;
> +}

So just one read_regs fuction is needed.  Which also would allow
read_regs to be removed from the ops struct since it's the same for both
chips.

> +
> +static const struct mcp23s08_ops mcp23008_ops = {
> +	.read		= mcp23008_read,
> +	.write		= mcp23008_write,
> +	.read_regs	= mcp23008_read_regs,
> +};
> +