Re: [RFC] Dummy GPIO driver for use with SPI

On Fri, Dec 12, 2008 at 01:39:45PM -0800, Trent Piepho wrote:

On Fri, 12 Dec 2008, Anton Vorontsov wrote:

quoted

On Fri, Dec 12, 2008 at 11:59:13AM -0500, Steven A. Falco wrote:

quoted

What do you think about having a mechanism to specify that some
SPI slaves have a chip select, while others don't have to have a
chip select managed by the SPI subsystem?

Um.. do you know that you can pass '0' as a GPIO?

For example,

spi-controller {
	gpios = <&pio1 1 0	/* cs0 */
		 0		/* cs1, no GPIO */
		 &pio2 2 0>;	/* cs2 */

It's ok the that middle specifier is only one word instead of three?  Seems
like "0 0 0" would be better, so all the specifiers are the same size.

quoted

		normal case;
	} else if (gpio == -EEXIST) {

Isn't EEXIST (pathname already exists) backward?

In my thinking it's "the GPIO is specified (exists in the list), but
it's would be an error if you try to use it". So EEXIST.

Seems like ENOENT would
be the right error code.  Except that's used for reading past the end...
Maybe a reading past the end should be EINVAL or EBADF?

Or return ENODEV for the 'hole' cell?  Or ENOLINK?

I'd say it's a matter of taste, none of the errors are actually
appropriate. An appropriate errno value would be EHOLEINALIST,
but we don't have it.

Thanks,

-- 
Anton Vorontsov
email: cbouatmailru@gmail.com
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