linux-kernel - Re: [PATCH v12 7/7] nvmem: core: Expose cells through sysfs

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Message-ID: <490c6740-06cb-9ee6-ca8c-3ab404109344@linaro.org>
Date:   Wed, 11 Oct 2023 10:26:43 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Michael Walle <michael@...le.cc>,
        Rafał Miłecki <rafal@...ecki.pl>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Robert Marko <robert.marko@...tura.hr>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Luka Perkov <luka.perkov@...tura.hr>,
        Randy Dunlap <rdunlap@...radead.org>,
        Chen-Yu Tsai <wenst@...omium.org>,
        Daniel Golle <daniel@...rotopia.org>
Subject: Re: [PATCH v12 7/7] nvmem: core: Expose cells through sysfs



On 11/10/2023 09:58, Miquel Raynal wrote:
> Hi Srinivas,
> 
> srinivas.kandagatla@...aro.org wrote on Wed, 11 Oct 2023 09:45:11 +0100:
> 
>> On 11/10/2023 09:33, Miquel Raynal wrote:
>>> Hi Srinivas,
>>>
>>> srinivas.kandagatla@...aro.org wrote on Wed, 11 Oct 2023 09:27:20 +0100:
>>>    
>>>> On 11/10/2023 08:15, Miquel Raynal wrote:
>>>>>>> +
>>>>>>> +	nvmem_cells_group.bin_attrs = cells_attrs;
>>>>>>> +
>>>>>>> +	ret = devm_device_add_groups(&nvmem->dev, nvmem_cells_groups);
>>>>>>> +	if (ret)
>>>>>>> +		goto unlock_mutex;
>>>>>> This is going to create groups after the nvmem device is added, isn't this going to be problem with user space notifications?
>>>>> Greg said it was not. I hope I understood correctly 😄
>>>>>
>>>>> And anyway, cells have never been available to userspace, so there is
>>>>> nothing userspace might expect yet?
>>>> I agree, but once we add sysfs uapi then this is going to change.
>>>
>>> Can you elaborate? I'm not sure I follow you here. Is there still a
>>> problem you fear or you think it's okay?
>>>    
>> Now that we add cells to sysfs.
>> AFAIU, By the time the userspace sees the udev event from this device we might not have cells populated.
> 
> Yes, but why would this be a problem?
> 
It will be problem if the userspace is using things like libudev to act 
on these events. There seems to be some caching of attributes in udev 
during event more info 
http://www.kroah.com/log/blog/2013/06/26/how-to-create-a-sysfs-file-correctly/


--srini

> Thanks,
> Miquèl