From 644e9cbbe3fc032cc92d0936057e166a994dc246 Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Thu, 26 Jan 2012 00:09:05 +0100 Subject: Add driver auto probing for x86 features v4 There's a growing number of drivers that support a specific x86 feature or CPU. Currently loading these drivers currently on a generic distribution requires various driver specific hacks and it often doesn't work. This patch adds auto probing for drivers based on the x86 cpuid information, in particular based on vendor/family/model number and also based on CPUID feature bits. For example a common issue is not loading the SSE 4.2 accelerated CRC module: this can significantly lower the performance of BTRFS which relies on fast CRC. Another issue is loading the right CPUFREQ driver for the current CPU. Currently distributions often try all all possible driver until one sticks, which is not really a good way to do this. It works with existing udev without any changes. The code exports the x86 information as a generic string in sysfs that can be matched by udev's pattern matching. This scheme does not support numeric ranges, so if you want to handle e.g. ranges of model numbers they have to be encoded in ASCII or simply all models or families listed. Fixing that would require changing udev. Another issue is that udev will happily load all drivers that match, there is currently no nice way to stop a specific driver from being loaded if it's not needed (e.g. if you don't need fast CRC) But there are not that many cpu specific drivers around and they're all not that bloated, so this isn't a particularly serious issue. Originally this patch added the modalias to the normal cpu sysdevs. However sysdevs don't have all the infrastructure needed for udev, so it couldn't really autoload drivers. This patch instead adds the CPU modaliases to the cpuid devices, which are real devices with full support for udev. This implies that the cpuid driver has to be loaded to use this. This patch just adds infrastructure, some driver conversions in followups. Thanks to Kay for helping with some sysfs magic. v2: Constifcation, some updates v4: (trenn@suse.de): - Use kzalloc instead of kmalloc to terminate modalias buffer - Use uppercase hex values to match correctly against hex values containing letters Cc: Dave Jones Cc: Kay Sievers Cc: Jen Axboe Cc: Herbert Xu Cc: Huang Ying Cc: Len Brown Signed-off-by: Andi Kleen Signed-off-by: Thomas Renninger Acked-by: H. Peter Anvin Signed-off-by: Greg Kroah-Hartman --- include/linux/mod_devicetable.h | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) (limited to 'include/linux/mod_devicetable.h') diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h index b29e7f6f8fa5..cff2cc08f45a 100644 --- a/include/linux/mod_devicetable.h +++ b/include/linux/mod_devicetable.h @@ -571,4 +571,25 @@ struct amba_id { #endif }; +/* + * Match x86 CPUs for CPU specific drivers. + * See documentation of "x86_match_cpu" for details. + */ + +struct x86_cpu_id { + __u16 vendor; + __u16 family; + __u16 model; + __u16 feature; /* bit index */ + kernel_ulong_t driver_data; +}; + +#define X86_FEATURE_MATCH(x) \ + { X86_VENDOR_ANY, X86_FAMILY_ANY, X86_MODEL_ANY, x } + +#define X86_VENDOR_ANY 0xffff +#define X86_FAMILY_ANY 0 +#define X86_MODEL_ANY 0 +#define X86_FEATURE_ANY 0 /* Same as FPU, you can't test for that */ + #endif /* LINUX_MOD_DEVICETABLE_H */ -- cgit v1.2.3