Re: [PATCH net-next v4 02/13] net: wwan: t7xx: Add control DMA interface

[Sergey Ryazanov <ryazanov.s.a@gmail.com>]

Hello Ricardo,

On Wed, Jan 19, 2022 at 1:22 AM Martinez, Ricardo
<ricardo.martinez@linux.intel.com> wrote:
> On 1/18/2022 6:13 AM, Ilpo Järvinen wrote:
>> On Thu, 13 Jan 2022, Ricardo Martinez wrote:
> ...
>>> +#define CLDMA_NUM 2
>> I tried to understand its purpose but it seems that only one of the
>> indexes is used in the arrays where this define gives the size? Related to
>> this, ID_CLDMA0 is not used anywhere?
>
> The modem HW has 2 CLDMAs, idx 0 for the app processor (SAP) and idx 1
> for the modem (MD).
>
> CLDMA_NUM is defined as 2 to reflect the HW capabilities but mainly to
> have a cleaner upcoming patches, which will use ID_CLDMA0.
>
> If having array's of size 1 is not a problem then we can define
> CLDMA_NUM as 1 and play with the CLDMA indexes.

Please keep CLDMA_NUM defined as 2. Especially if you have a plan for
further driver development. Saving a few bytes in the structure for a
short term is not worth the jungling with indexes, possible errors and
further rework. Just document them as suggested by Ilpo and mark idx 0
as unused at the moment.

BTW, did you consider to define the cldma_id enum something like this:

/**
 * ...
 * @CLDMA_ID_AP: ... (unused ATM)
 * @CLDMA_ID_MD: ...
 */
enum cldma_id {
    CLDMA_ID_AP = 0,
    CLDMA_ID_MD = 1,

    CLDMA_NUM
};

This way elements will be self descriptive as well as CLDMA_NUM value
will be less puzzled.

-- 
Sergey