On Tue, Dec 7, 2010 at 2:34 PM, Peter Tyser <pty...@xes-inc.com> wrote: > <snip> > >> > You could do the same thing to the U-Boot pca953x driver. >> > Eg at the top you could add: >> > #ifdef CONFIG_PCA953X_16BIT >> > #define NGPIO = 16 >> > #else >> > #define NGPIO = 8 >> > #endif >> >> I have a small problem with this due to the fact that we have some >> designs here that use a pca9534 and a pca9539. Having a compile-time >> conditional like this means you can only support one or the other. >> Linux can handle this because it's actually got a structure that >> contains the 8 vs 16 whereas u-boot only has the address an no other >> information. Any suggestions on handling this would be welcome. > > Some ideas: > - Do a series of byte reads and determine the number of GPIOs based on > mirroring of registers, or reads failing if they are past the "end" of > the device. eg reading register 4 on a 8-bit device might fail, or wrap > around and return the same data as register 0.
Hmm, I can see problems ahead for that approach. > - Make CONFIG_PCA953X_16BIT an array that lists which I2C address > support 16 bits, then use it to determine which devices are 8 vs 16 bits > dynamically. I think this is probably the best option. It shouldn't be that hard to implement. > - Convert the driver to be more intelligent. eg add an interface like > pca953x_add_dev(u8 addr, u8 bits) which each board calls to add a device > to a list of devices maintained by the pca953x driver. Eg in my board > code I'd do: > pca953x_add_dev(0x18, 8); > pca953x_add_dev(0x1c, 8); > pca953x_add_dev(0x1e, 8); > pca953x_add_dev(0x1f, 8); I like the idea but I was hoping not to affect other boards, but if people are on-board and able to test I could look into this option. Another approach I though about was having a global variable which would default to 8 but could be modified via an appropriate setter prior to making calls to pca953x_set_xyz. _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
