netdev - Re: [PATCH v2 4/4] wcn36xx: Add debugfs entry to read firmware feature strings

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Date:   Wed, 27 Jul 2022 11:41:48 +0100
From:   Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To:     Kalle Valo <kvalo@...nel.org>
Cc:     loic.poulain@...aro.org, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, wcn36xx@...ts.infradead.org,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v2 4/4] wcn36xx: Add debugfs entry to read firmware
 feature strings

On 27/07/2022 11:31, Kalle Valo wrote:
> Bryan O'Donoghue <bryan.odonoghue@...aro.org> writes:

>> +static ssize_t read_file_firmware_feature_caps(struct file *file,
>> +					       char __user *user_buf,
>> +					       size_t count, loff_t *ppos)
>> +{
>> +	struct wcn36xx *wcn = file->private_data;
>> +	unsigned long page = get_zeroed_page(GFP_KERNEL);
>> +	char *p = (char *)page;
>> +	int i;
>> +	int ret;
>> +
>> +	if (!p)
>> +		return -ENOMEM;
>> +
>> +	mutex_lock(&wcn->hal_mutex);
>> +	for (i = 0; i < MAX_FEATURE_SUPPORTED; i++) {
>> +		if (wcn36xx_firmware_get_feat_caps(wcn->fw_feat_caps, i)) {
>> +			p += sprintf(p, "%s\n",
>> +				     wcn36xx_firmware_get_cap_name(i));
>> +		}
>> +	}
>> +	mutex_unlock(&wcn->hal_mutex);
>> +
>> +	ret = simple_read_from_buffer(user_buf, count, ppos, (char *)page,
>> +				      (unsigned long)p - page);
>> +
>> +	free_page(page);
>> +	return ret;
>> +}
> 
> Why not use the normal use kzalloc() and kfree()? That way you would not
> need a separate page variable. What's the benefit from
> get_zeroed_page()?


TBH I did a copy/paste here from another driver... I forget which
> 
> Also I don't see any checks for a memory allocation failure.
> 

its there

char *p = (char*) page;

if (!p)
     return -ENOMEM;

I can V2 this for kzalloc and kfree if you prefer though

---
bod