linux-kernel - Re: [PATCH] serial: 8250_lpss: Release Quark MSI vectors on exit

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Message-ID: <bec9b233-5069-c54a-4c11-9e6c33e7ef9a@siemens.com>
Date:   Thu, 5 Jan 2017 08:03:13 +0100
From:   Jan Kiszka <jan.kiszka@...mens.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] serial: 8250_lpss: Release Quark MSI vectors on exit

On 2017-01-05 06:25, Christoph Hellwig wrote:
> On Wed, Jan 04, 2017 at 11:46:58PM +0100, Jan Kiszka wrote:
>>> I NAKed already third patch related to PCI managed resources (couple
>>> of those regarding to pci_irq_* API)/
>>>
>>
>> Ah, there are resources that are managed without being allocated
>> explicitly that way. Hmm, not very intuitive. Are MSI / MSI-X vectors
>> the only such cases?
> 
> MSI/MSI-X resources are not managed that way and an explicit call to
> pci_free_irq_vectors is required from the API standpoint.  It might not
> actually free memory in many cases, but it still is a symmetric API.
> 

Andy is referring to the following:
- pcim_enable_device registers pci_devres with the devres subsystem
- on device release, devres_release_all is invoked, and that calls
  pcim_release
- the latter will invoke pci_disable_msi and pci_disable_msix if any of
  them is enabled

The user will still call the same pci_msi_enable, pci_alloc_irq_vectors
etc., but they are now "magically" managed with pcim_enable_device being
used. Same for pci_request_region.

Jan

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