On Wed, Jun 4, 2008 at 8:41 PM, David Gibson <[EMAIL PROTECTED]> wrote: > On Wed, Jun 04, 2008 at 09:19:42PM -0500, Josh Boyer wrote: >> On Wed, 4 Jun 2008 10:43:51 -0500 >> Scott Wood <[EMAIL PROTECTED]> wrote: >> >> > On Wed, Jun 04, 2008 at 10:24:15AM -0500, Timur Tabi wrote: >> > > Stefan Roese wrote: >> > > > I'm wondering what is currently recommended in the I2C device tree >> > > > nodes? The >> > > > current IBM I2C driver (i2c-ibm_iic.c) checks "index" and most FSL dts >> > > > files >> > > > use "cell-index". Some 4xx dts files implement "cell-index" some have >> > > > no >> > > > index at all. >> > > > >> > > > So what should be used here. Please advise and I'll prepare a patch >> > > > for it. >> > > >> > > I just posted a patch for the FSL I2C driver to check for cell-index. >> > > I'm under >> > > the impression that cell-index is the standard for enumerating devices >> > > in the >> > > device tree. >> > >> > No, it's the standard for correlating devices with portions of a shared >> > register block elsewhere. Your use in the I2C node is merely a hack to >> > deal with Linux wanting to deal with indices rather than pointers, >> > combined with a lack of a decent way to look up a device struct from the >> > device node. >> >> So if possible, I'd like to eliminate the *index stuff all together >> from the 4xx driver. The private data structure contains an idx >> parameter, but this can be populated based on probe order or something. >> >> >From a device tree perspective, index and cell-index are both >> incorrect. The IIC macros don't share register blocks with anything, >> are enumerated as unique instances per macro in the device tree, and >> should be able to be distinguished by "regs" and/or unit address. >> >> Does anyone disagree with that? > > Hear, hear. > > Aliases can also provide a reasonable way of enumerating devices, if > "reg" isn't suitable on its own. Though obviously, drivers will need > some sort of fallback if suitable aliases don't exist in the tree.
The fallback is to just let the i2c layer auto-assign an ID. The only reason I can think of to want to assign a specific id to an i2c bus is so that a userspace application can reference a specific bus. The drivers really shouldn't care. Cheers, g. -- Grant Likely, B.Sc., P.Eng. Secret Lab Technologies Ltd. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
