Re: [Xen-devel] [PATCH v7 05/28] xen/arm: ITS: Port ITS driver to Xen

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hi Vijay,

The only things I haven't check on this patch was the ITS command structure.

On 18/09/15 14:08, vijay.kilari@xxxxxxxxx wrote:
> +/* ITS command structure */
> +typedef union {

Can you please sort this union by command name in alphabetical order.
It's way easier to find a command in the list.

> +    u64 bits[4];
> +    struct __packed {
> +        uint8_t cmd;

NIT: Please stay consistent with usage of the type. You are using u8
everywhere within this union except here.

> +        uint8_t pad[7];

Why a padding of only 56 bits? Shouldn't it be 248 bits (i.e 31 * 8
bits) to fit all the command?

> +    } hdr;
> +    struct __packed {
> +        u8 cmd;
> +        u8 res1[3];
> +        u32 devid;
> +        u64 size:5;
> +        u64 res2:59;
> +        /* XXX: Though itt is 40 bit. Keep it 48 to avoid shift */
> +        u64 res3:8;

It's very confusing for the reviewer to see a mix of usage (u8 res1[n],
u64 res3:8) within the same structure.

The later (i.e u64 field:n) is the best to use because we can match
quickly the size with the spec.

> +        u64 itt:40;
> +        u64 res4:15;
> +        u64 valid:1;
> +        u64 res5;
> +    } mapd;

[..]

> +    struct __packed {
> +        u8 cmd;
> +        u8 res1[3];
> +        u32 devid;
> +        u32 event;
> +        u32 res2;
> +        u64 res3;
> +        u64 res4;
> +    } int_cmd;

Maybe you want to add the suffix _cmd to everyone to avoid having only
one because of C spec issue.

> +    struct __packed {
> +        u8 cmd;
> +        u8 res1[3];
> +        u32 devid;
> +        u32 event;
> +        u32 res2;
> +        u64 res3;
> +        u64 res4;
> +    } clear;
> +    struct __packed {
> +        u8 cmd;
> +        u8 res1[7];
> +        u64 res2;
> +        u16 res3;
> +        u32 ta;

It would have been better to have a full name or a description rather
than only a 2 letter field "ta". I won't ask for a documentation of this
field right now, but it would be a nice follow-up of this series.

> +        u16 res4;
> +        u64 res5;
> +    } sync;
> +} its_cmd_block;


Regards,

-- 
Julien Grall

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel