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SubjectRe: [PATCH 2/2] uacce: add uacce module
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Hi, Greg

On 2019/8/19 下午6:24, Greg Kroah-Hartman wrote:
>>>> +static int uacce_create_chrdev(struct uacce *uacce)
>>>> +{
>>>> + int ret;
>>>> +
>>>> + ret = idr_alloc(&uacce_idr, uacce, 0, 0, GFP_KERNEL);
>>>> + if (ret < 0)
>>>> + return ret;
>>>> +
>>> Shouldn't this function create the memory needed for this structure?
>>> You are relying ont he caller to do it for you, why?
>> I think you mean uacce structure here.
>> Yes, currently we count on caller to prepare uacce structure and call
>> uacce_register(uacce).
>> We still think this method is simpler, prepare uacce, register uacce.
>> And there are other system using the same method, like crypto
>> (crypto_register_acomp), nand, etc.
> crypto is not a subsystem to ever try to emulate :)
>
> You are creating a structure with a lifetime that you control, don't
> have someone else create your memory, that's almost never what you want
> to do. Most all driver subsystems create their own memory chunks for
> what they need to do, it's a much better pattern.
>
> Especially when you get into pointer lifetime issues...
OK, understand now, thanks for your patience.
will use this instead.
struct uacce_interface {
        char name[32];
        unsigned int flags;
        struct uacce_ops *ops;
};
struct uacce *uacce_register(struct device *dev, struct uacce_interface
*interface);
>>>> +}
>>>> +
>>>> +static int uacce_dev_match(struct device *dev, void *data)
>>>> +{
>>>> + if (dev->parent == data)
>>>> + return -EBUSY;
>>> There should be in-kernel functions for this now, no need for you to
>>> roll your own.
>> Sorry, do not find this function.
>> Only find class_find_device, which still require match.
> It is in linux-next, look there...
>
Suppose you mean the funcs: device_match_name,
device_match_of_node,device_match_devt etc.
Here we need dev->parent, there still no such func.

Thanks

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