On Sun, Jan 27, 2013 at 09:33:04PM +0530, Viresh Kumar wrote: > On 27 January 2013 21:12, Andrew Lunn <andrew@xxxxxxx> wrote: > > And how would the module get loaded? There is no hardware anchor to > > make the module load. No enumeration of some bus causing it to be > > loaded. In the ARM world, platform drivers are the norm. > > The way you do it now is by creating a platform device for it in your > arch/arm/mach-* directory. And you are passing an IOMEM resource too. > > I believe, normally we don't require any DT node or platform device from > arch/arm/mach-* for cpufreq drivers. This is something which should > always be initialized once it is selected in .config. What current happens is that most of the drivers use a late_initcall(): linux/drivers/cpufreq$ grep late_initcall * acpi-cpufreq.c:late_initcall(acpi_cpufreq_init); cpufreq-cpu0.c:late_initcall(cpu0_cpufreq_driver_init); exynos-cpufreq.c:late_initcall(exynos_cpufreq_init); longhaul.c:late_initcall(longhaul_init); p4-clockmod.c:late_initcall(cpufreq_p4_init); pcc-cpufreq.c:late_initcall(pcc_cpufreq_init); powernow-k7.c:late_initcall(powernow_init); powernow-k8.c:late_initcall(powernowk8_init); s5pv210-cpufreq.c:late_initcall(s5pv210_cpufreq_init); spear-cpufreq.c:late_initcall(spear_cpufreq_driver_init); speedstep-centrino.c:late_initcall(centrino_init); So when we have a multiplatform kernel with many of these drivers built in, all but one are going to notice they are not on the hardware they support, and return -ENODEV. By making it a platform driver, the kirkwood cpufreq driver will only get loaded on kirkwood systems, and won't slow down the boot for everybody else. Andrew -- To unsubscribe from this list: send the line "unsubscribe cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
