of_spi: add generic binding support to specify cs gpio
This will allow to use gpio for chip select with no modification in the driver binding When use the cs-gpios, the gpio number will be passed via the cs_gpio field and the number of chip select will automatically increased with max(hw cs, gpio cs). So if for example the controller has 2 CS lines, and the cs-gpios property looks like this: cs-gpios = <&gpio1 0 0> <0> <&gpio1 1 0> <&gpio1 2 0>; Then it should be configured so that num_chipselect = 4 with the following mapping: cs0 : &gpio1 0 0 cs1 : native cs2 : &gpio1 1 0 cs3 : &gpio1 2 0 Signed-off-by: NJean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com> Cc: devicetree-discuss@lists.ozlabs.org Cc: spi-devel-general@lists.sourceforge.net Signed-off-by: NRichard Genoud <richard.genoud@gmail.com> [grant.likely: fixed up type of cs count so min() can do type checking] Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>
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