Subject: Re: Subject: [PATCH v8] spi: Add PPC4xx SPI driver

From: "Steven A. Falco" <[email-masked]>
Date: Mon, 06 Jul 2009 12:19:44 -0400

David Brownell wrote:
> On Friday 26 June 2009, Steven A. Falco wrote:
>> +
>> +       /*
>> +        * If there are no chip selects at all, or if this is the special
>> +        * case of a non-existent (dummy) chip select, do nothing.
>> +        */
>> +
>> +       if (!hw->master->num_chipselect || hw->gpios[cs] == -EEXIST)
>> +               return;
>> +
> 
> I'm going to send this in, but please send a followup
> patch making all this "non-existent (dummy) chip select"
> stuff use the SPI_NO_CS flag.
> 

Not sure yet how this will work.  GPIOs are detected during probe.
of_get_gpio_flags() will return EEXIST for devices without a CS,
and will return the gpio number for devices with a CS, but probe
doesn't (currently) know anything about "struct spi_device".

In fact, the devices don't exist until spi_bitbang_start is called,
near the end of the probe.  So, I've not figured out how the probe
routine will set the new SPI_NO_CS flag on a per-device basis.

There is one example of a ppc board calling spi_register_board_info,
but even that board doesn't really use it, if a device tree exists.

> 
>> +       /*
>> +        * A count of zero implies a single SPI device without any chip-select.
>> +        * Note that of_gpio_count counts all gpios assigned to this spi master.
>> +        * This includes both "null" gpio's and real ones.
>> +        */
> 
> 
>