linux-kernel - Re: [PATCH 2/2] uacce: add uacce module

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Message-ID: <0f7c6241-2028-76e7-0314-8b99cd353bd6@linaro.org>
Date:   Tue, 20 Aug 2019 20:36:50 +0800
From:   zhangfei <zhangfei.gao@...aro.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "zhangfei.gao@...mail.com" <zhangfei.gao@...mail.com>
Cc:     Arnd Bergmann <arnd@...db.de>, linux-accelerators@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, Kenneth Lee <liguozhu@...ilicon.com>,
        Zaibo Xu <xuzaibo@...wei.com>,
        Zhou Wang <wangzhou1@...ilicon.com>
Subject: Re: [PATCH 2/2] uacce: add uacce module

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