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

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Date:   Fri, 19 Feb 2021 15:40:05 +0100
From:   Robert Richter <rric@...nel.org>
To:     Dejin Zheng <zhengdejin5@...il.com>
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 18.02.21 23:04:55, Dejin Zheng wrote:
> Introduce pcim_alloc_irq_vectors(), a device-managed version of
> pci_alloc_irq_vectors(). Introducing this function can simplify
> the error handling path in many drivers.
> 
> And use pci_free_irq_vectors() to replace some code in pcim_release(),
> they are equivalent, and no functional change. It is more explicit
> that pcim_alloc_irq_vectors() is a device-managed function.
> 
> Suggested-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> Signed-off-by: Dejin Zheng <zhengdejin5@...il.com>
> ---
> v3 -> v4:
> 	- No change
> v2 -> v3:
> 	- Add some commit comments for replace some codes in
> 	  pcim_release() by pci_free_irq_vectors().
> v1 -> v2:
> 	- Use pci_free_irq_vectors() to replace some code in
> 	  pcim_release().
> 	- Modify some commit messages.
> 
>  drivers/pci/pci.c   | 33 +++++++++++++++++++++++++++++----
>  include/linux/pci.h |  3 +++
>  2 files changed, 32 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index b67c4327d307..db799d089c85 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -1969,10 +1969,7 @@ static void pcim_release(struct device *gendev, void *res)
>  	struct pci_devres *this = res;
>  	int i;
>  
> -	if (dev->msi_enabled)
> -		pci_disable_msi(dev);
> -	if (dev->msix_enabled)
> -		pci_disable_msix(dev);
> +	pci_free_irq_vectors(dev);
>  
>  	for (i = 0; i < DEVICE_COUNT_RESOURCE; i++)
>  		if (this->region_mask & (1 << i))
> @@ -2054,6 +2051,34 @@ void pcim_pin_device(struct pci_dev *pdev)
>  }
>  EXPORT_SYMBOL(pcim_pin_device);
>  
> +/**
> + * pcim_alloc_irq_vectors - a device-managed pci_alloc_irq_vectors()
> + * @dev:		PCI device to operate on
> + * @min_vecs:		minimum number of vectors required (must be >= 1)
> + * @max_vecs:		maximum (desired) number of vectors
> + * @flags:		flags or quirks for the allocation
> + *
> + * Return the number of vectors allocated, (which might be smaller than
> + * @max_vecs) if successful, or a negative error code on error. If less
> + * than @min_vecs interrupt vectors are available for @dev the function
> + * will fail with -ENOSPC.
> + *
> + * It depends on calling pcim_enable_device() to make IRQ resources
> + * manageable.
> + */
> +int pcim_alloc_irq_vectors(struct pci_dev *dev, unsigned int min_vecs,
> +				unsigned int max_vecs, unsigned int flags)
> +{
> +	struct pci_devres *dr;
> +
> +	dr = find_pci_dr(dev);
> +	if (!dr || !dr->enabled)
> +		return -EINVAL;
> +
> +	return pci_alloc_irq_vectors(dev, min_vecs, max_vecs, flags);
> +}
> +EXPORT_SYMBOL(pcim_alloc_irq_vectors);

If it is just about having a pcim-* counterpart why not just an inline
function like the one below.

> +
>  /*
>   * pcibios_add_device - provide arch specific hooks when adding device dev
>   * @dev: the PCI device being added
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 86c799c97b77..d75ba85ddfc5 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1818,6 +1818,9 @@ pci_alloc_irq_vectors(struct pci_dev *dev, unsigned int min_vecs,
>  					      NULL);
>  }
>  
> +int pcim_alloc_irq_vectors(struct pci_dev *dev, unsigned int min_vecs,
> +				unsigned int max_vecs, unsigned int flags);
> +

static inline int pcim_alloc_irq_vectors(struct pci_dev *dev,
	unsigned int min_vecs, unsigned int max_vecs, unsigned int flags)
{
	if (!pci_is_managed(dev, min_vecs, max_vecs, flags))
		return -EINVAL;

	return pci_alloc_irq_vectors(dev, min_vecs, max_vecs, flags);
}

All those stub functions with EXPORT_SYMBOLS etc. could be dropped
then.

With some macro magic added a list of functions could easily being
created that are already managed but just need a pcim* counterpart.

-Robert

>  /* Include architecture-dependent settings and functions */
>  
>  #include <asm/pci.h>
> -- 
> 2.25.0
>