[PATCH 2/2] uacce: add uacce module

zhangfei zhangfei.gao at linaro.org
Sat Aug 24 22:53:01 AEST 2019

On 2019/8/20 下午10:33, Greg Kroah-Hartman wrote:
> On Tue, Aug 20, 2019 at 08:36:50PM +0800, zhangfei wrote:
>> 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);
> What?  Why do you need a structure?  A pointer to the name and the ops
> should be all that is needed, right?
We are thinking transfer structure will be more flexible.
And modify api later would be difficult, requiring many drivers modify 
Currently parameters need a flag, a pointer to the name, and ops, but in 
case more requirement from future drivers usage.
Also refer usb_register_dev, sdhci_pltfm_init etc, and the structure 
para can be set as static.
> And 'dev' here is a pointer to the parent, right?  Might want to make
> that explicit in the name of the variable :)
Yes, 'dev' is parent, will change to 'pdev', thanks.
>>>>>> +
>>>>>> +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.
> You should NEVER be matching on a parent.  If so, your use of the driver
> model is wrong :)
> Remind me to really review the use of the driver core code in your next
> submission of this series please, I think it needs it.

OK, thanks Greg.

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