linux-kernel - Re: [PATCH v4 1/4] PCI: Introduce pcim_alloc_irq

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Message-ID: <20210222151415.GA896979@nuc8i5>
Date:   Mon, 22 Feb 2021 23:14:15 +0800
From:   Dejin Zheng <zhengdejin5@...il.com>
To:     Robert Richter <rric@...nel.org>
Cc:     corbet@....net, jarkko.nikula@...ux.intel.com,
        andriy.shevchenko@...ux.intel.com, mika.westerberg@...ux.intel.com,
        bhelgaas@...gle.com, wsa@...nel.org, linux-doc@...r.kernel.org,
        linux-i2c@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/4] PCI: Introduce pcim_alloc_irq_vectors()

On Mon, Feb 22, 2021 at 11:56:08AM +0100, Robert Richter wrote:
> On 20.02.21 00:46:49, Dejin Zheng wrote:
> > > On 18.02.21 23:04:55, Dejin Zheng wrote:
> 
> > > > +	if (!dr || !dr->enabled)
> > here checks whether the pci device is enabled.
> 
> What is the purpose of this? The device "is_managed" or not.
>
The device is managed or not by check whether "dr" is NULL. And
check the "dr->enabled" is for the PCI device enable. I think it
may not make sense to apply for irq vectors when PCI device is not
enabled.

PCI device enable by call pci_enable_device() function, this function
initialize device before it's used by a driver. Ask low-level code
to enable I/O and memory. Wake up the device if it was suspended.

So I think it might be better to return to failure when it is found
the PCI device is not enabled in the pcim_alloc_irq_vectors() function.
It can facilitate developers to find problems as soon as possible.

BR,
Dejin
> -Robert