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SubjectRE: [PATCH v9 5/6] usb:cdns3 Add Cadence USB3 DRD Driver
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Hi Felipe

>>> +
>>> +static int cdns3_idle_init(struct cdns3 *cdns)
>>> +{
>>> + struct cdns3_role_driver *rdrv;
>>> +
>>> + rdrv = devm_kzalloc(cdns->dev, sizeof(*rdrv), GFP_KERNEL);
>>> + if (!rdrv)
>>> + return -ENOMEM;
>>> +
>>> + rdrv->start = cdns3_idle_role_start;
>>> + rdrv->stop = cdns3_idle_role_stop;
>>> + rdrv->state = CDNS3_ROLE_STATE_INACTIVE;
>>> + rdrv->suspend = NULL;
>>> + rdrv->resume = NULL;
>>> + rdrv->name = "idle";
>>
>>why don't you use the mux framework for this? This looks a bit fishy
>>too. Why do you have your own driver registration structure for your
>>driver only?
>>
>
>I assume you mean interface defined in include/linux/usb/role.h.
>It's quite new framework and probably was added after I've start implementing cdns3 driver.
>At first glance it's look that I could use it.

I've started integrating driver with role switch framework.

Even if I use role switch interface , I still need this internal driver registration.
It's convenient to use fallowing structure.

struct cdns3_role_driver {
int (*start)(struct cdns3 *cdns);
void (*stop)(struct cdns3 *cdns);
int (*suspend)(struct cdns3 *cdns, bool do_wakeup);
int (*resume)(struct cdns3 *cdns, bool hibernated);
const char *name;
#define CDNS3_ROLE_STATE_INACTIVE 0
#define CDNS3_ROLE_STATE_ACTIVE 1
int state;
};

Driver can supports: only Host, only Device or DRD - depending on configuration.

If current configuration support only Host then driver assigns:
rdrv_host->start = __cdns3_host_init;
rdrv_host->stop = cdns3_host_exit;

cdns->roles[CDNS3_ROLE_HOST] = rdrv_host
cdns->roles[CDNS3_ROLE_GADGET = NULL;
if support only Device then:
rdrv_dev->start = __cdns3_ gadget _init;
rdrv_dev->stop = cdns3_ gadget _exit;
cdns->roles[CDNS3_ROLE_HOST] = NULL;
for DRD:
cdns->roles[CDNS3_ROLE_HOST = rdrv_host;
cdns->roles[CDNS3_ROLE_GADGET] = rdrv_dev;

So for DRD we will have both filled, but for only Device or Host we
will have filled single element of array.

With such array we can easily start/stop role by
if (!cdns->roles[role])
not supported by configuration.
else
cdns->roles[role]->start / cdns->roles[role]->stop

I don't need any extra: switch instruction or #ifdef statement.

The name cdns3_role_driver can be misleading.
Driver doesn't register the driver but rather the interface to Device/Host.

Maybe I should change this name to cdns3_role_interface or cdns3_role_action ?

Now I have my private enum:
enum cdns3_roles {
CDNS3_ROLE_IDLE = 0,
CDNS3_ROLE_HOST,
CDNS3_ROLE_GADGET,
CDNS3_ROLE_END,
};

I think I could replace it with usb_role. I need one extra state for IDLE but
Instead of CDNS3_ROLE_IDLE I can use USB_ROLE_NONE.

It should little simplify the driver and improve readability.

Do you have any comments or suggestion ?

Cheers,
Pawel

>
>>> +
>>> + cdns->roles[CDNS3_ROLE_IDLE] = rdrv;
>>> +
>>> + return 0;
>>> +}
>>> +

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