On Fri, Oct 20, 2017 at 05:50:57PM +0200, Takashi Iwai wrote:
On Fri, 20 Oct 2017 17:46:49 +0200, Vinod Koul wrote:
--- a/include/linux/mod_devicetable.h +++ b/include/linux/mod_devicetable.h @@ -228,6 +228,13 @@ struct hda_device_id { unsigned long driver_data; };
+struct sdw_device_id {
- __u16 mfg_id;
- __u16 part_id;
- __u8 class_id;
- kernel_ulong_t driver_data;
Better to think of alignment.
sorry not quite clear, do you mind elaborating which ones to align?
kernel_ulong_t may be aligned to 4 or 8 bytes, depending on architecture, so there can be a hole between class_id and driver_data. It's not an ABI, so we don't have to care too much, but it's still something exposed, hence better to be conscious about alignment.
ah :) is that why hda is unsigned long :) Btw doesnt that cause compat issues, should we not do something like u64 here?
Oh, don't take the HD-audio case as a good reference, it's a bad guy ;) In the case of hda, the definition isn't really exposed.
Not really it is for ext-hda codecs
The alignment doesn't matter whether it's unsigned long or kernel_ulong_t. It's a generic issue when you define some struct and expose it. In a safer side, you can put the enough pad bytes so that the long field is aligned in 8 bytes. Or use packed struct. Or you can just ignore and let it be so, but aware of the possible holes in your code.
that makes sense, I can add some reserved fields for padding here to fix and retain the kernel_ulong_t then