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SubjectRe: [PATCH v5 4/7] PCI/sysfs: Allow userspace to query and set device reset mechanism
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Hi Krzysztof,

On 6/6/21 7:58 AM, Krzysztof Wilczyński wrote:
> External email: Use caution opening links or attachments
>
>
> Hi Amey and Shanker,
>
> [...]
>> +static ssize_t reset_method_show(struct device *dev,
>> + struct device_attribute *attr,
>> + char *buf)
>> +{
>> + struct pci_dev *pdev = to_pci_dev(dev);
>> + ssize_t len = 0;
>> + int i, prio;
>> +
>> + for (prio = PCI_RESET_METHODS_NUM; prio; prio--) {
>> + for (i = 0; i < PCI_RESET_METHODS_NUM; i++) {
>> + if (prio == pdev->reset_methods[i]) {
>> + len += sysfs_emit_at(buf, len, "%s%s",
>> + len ? "," : "",
>> + pci_reset_fn_methods[i].name);
>> + break;
>> + }
>> + }
>> +
>> + if (i == PCI_RESET_METHODS_NUM)
>> + break;
>> + }
>> +
>> + return len;
>> +}
> Make sure to include trailing newline when exposing values through the
> sysfs object to the userspace in the above show() function.

Agree new line is needed. Will fix it.
> [...]
>> +static ssize_t reset_method_store(struct device *dev,
>> + struct device_attribute *attr,
>> + const char *buf, size_t count)
> [...]
>> +
>> + while ((name = strsep((char **)&buf, ",")) != NULL) {
> [...]
>
> This is something that I wonder could benefit from the following:
>
> char *options, *end;
>
> if (count >= (PAGE_SIZE - 1))
> return -EINVAL;
>
> options = kstrndup(buf, count, GFP_KERNEL);
> if (!options)
> return -ENOMEM;
>
> while ((name = strsep(&options, ",")) != NULL) {
> ...
> }
>
> ...
>
> kfree(options);
>
> Why? To avoid changing the string buffer that has been passed to
> reset_method_store() as strsep() while parsing will update the content
> of the buffer. The cast to (char **), aside of most definitely allowing
> to suppress the probable compiler warning, will also allow for what
> should be a technically a constant string (to which we got a pointer to)
> to be modified. I am not sure how much could this be of a problem, but
> I would try not to do it, if possible.

Thanks, will use temporary buffer for parsing string.
>
> [...]
>> +set_reset_methods:
>> + memcpy(pdev->reset_methods, reset_methods, sizeof(reset_methods));
>> + return count;
>> +}
>> +
>> +static DEVICE_ATTR_RW(reset_method);
> A small nitpikc: customary there is no space (a newline) between the
> function and the macro, the macro follows immediately after.

Will fix it.
> Krzysztof

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