On Wed, May 27, 2009 at 03:05:58PM -0600, Grant Likely wrote: > On Wed, May 27, 2009 at 2:52 PM, Mark Brown > <[email protected]> wrote: > > On Wed, May 27, 2009 at 08:29:10PM +0100, Russell King wrote: > >> On Wed, May 27, 2009 at 02:08:42PM -0500, Scott Wood wrote: > > > >> > I'm not talking about platform specific code, I'm talking about code to > >> > retrieve information about a device from the device tree. There would > >> > not be separate instances of this for "platforms X, Y and Z", just one > >> > of_platform binding in each driver. It's no different than having a > >> > platform bus binding, except in the data structures used. > > > >> I really don't see what OF buys us then, apart from additional dependencies > >> that have to be correct for the kernel to work. I can only see > >> disadvantages > >> if all OF is, is a way to pass some file to the kernel to (effectively) > >> tell > >> it which drivers to use. > > > > The main selling points of the device tree AFAICT are that some > > platforms have to use it it anyway due to the native OS and firmware for > > the platform use it, the possibility of using the same device tree with > > more than one OS (modulo unrepresentable holes) and the fact that some > > people find it more convenient to use than straight data tables > > (personally I find the two approaches to be much of a muchness there). > > Perhaps I'm missing something, though? > > Here are some that I've find useful: > > There is the advantage that it decouples the machine description from > the kernel code, which in turn seems to encourage code reuse. There > has been a significant decrease in the amount of platform specific > code in powerpc since the switch to FDT booting. > > There is the advantage of easy multiplatform support. I regularly > build a single kernel image which boots on all my MPC5200 boards, and > on my MPC83xx boards.
That is not necessarily an advantage of a device tree. On ARM you can also build a kernel which runs on 20+ PXA platforms at the same time. (And I'm sure it can be done to even support say i.MX and PXA at the same time, but this is another story) Sascha -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ devicetree-discuss mailing list [email protected] https://ozlabs.org/mailman/listinfo/devicetree-discuss
