linux-kernel - Re: [PATCH v10 2/8] PCI: Add new array for keeping track of ordering of reset methods

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Date:   Wed, 28 Jul 2021 13:08:36 -0500
From:   Shanker R Donthineni <sdonthineni@...dia.com>
To:     Amey Narkhede <ameynarkhede03@...il.com>,
        Bjorn Helgaas <helgaas@...nel.org>
CC:     <alex.williamson@...hat.com>,
        Raphael Norwitz <raphael.norwitz@...anix.com>,
        <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <kw@...ux.com>, Sinan Kaya <okaya@...nel.org>,
        Len Brown <lenb@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>
Subject: Re: [PATCH v10 2/8] PCI: Add new array for keeping track of ordering
 of reset methods

Hi Amey,

On 7/28/21 12:45 PM, Amey Narkhede wrote:
>>> +   BUILD_BUG_ON(ARRAY_SIZE(pci_reset_fn_methods) != PCI_NUM_RESET_METHODS);
>>>
>>>     might_sleep();
>>>
>>> -   rc = pci_dev_specific_reset(dev, 1);
>>> -   if (rc != -ENOTTY)
>>> -           return rc;
>>> -   rc = pcie_reset_flr(dev, 1);
>>> -   if (rc != -ENOTTY)
>>> -           return rc;
>>> -   rc = pci_af_flr(dev, 1);
>>> -   if (rc != -ENOTTY)
>>> -           return rc;
>>> -   rc = pci_pm_reset(dev, 1);
>>> -   if (rc != -ENOTTY)
>>> -           return rc;
>>> +   for (i = 1; i < PCI_NUM_RESET_METHODS; i++) {
>>> +           rc = pci_reset_fn_methods[i].reset_fn(dev, 1);
>>> +           if (!rc)
>>> +                   reset_methods[n++] = i;
>> Why do we need this local reset_methods[] array?  Can we just fill
>> in dev->reset_methods[] directly and skip the memcpy() below?
>>
> This is for avoiding caching of previously supported reset methods.
> Is it okay if I use memset(dev->reset_methods, 0,
> sizeof(dev->reset_methods)) instead to clear the values in
> dev->reset_methods?

Clearing the array before the loop might a better option, we can get rid of a local variable.

void pci_init_reset_methods(struct pci_dev *dev)
{
        int i, n, rc;

        BUILD_BUG_ON(ARRAY_SIZE(pci_reset_fn_methods) != PCI_NUM_RESET_METHODS);

        might_sleep();

        memset(dev->reset_methods, 0x0, sizeof(reset_methods));

        n = 0;
        for (i = 1; i < PCI_NUM_RESET_METHODS; i++) {
                rc = pci_reset_fn_methods[i].reset_fn(dev, 1);
                if (!rc)
                        dev->reset_methods[n++] = i;
                else if (rc != -ENOTTY)
                        break;
        }
}