Re: [Xen-devel] [PATCH v1 03/21] MSI: Remove the redundant irq_set_chip_data()

[Lucas Stach <l.stach@xxxxxxxxxxxxxx>]

Am Dienstag, den 16.09.2014, 09:30 +0800 schrieb Yijing Wang:
> On 2014/9/15 22:00, Lucas Stach wrote:
> > Am Freitag, den 05.09.2014, 18:09 +0800 schrieb Yijing Wang:
> >> Currently, pcie-designware, pcie-rcar, pci-tegra drivers
> >> use irq chip_data to save the msi_chip pointer. They
> >> already call irq_set_chip_data() in their own MSI irq map
> >> functions. So irq_set_chip_data() in arch_setup_msi_irq()
> >> is useless.
> >>
> >> Signed-off-by: Yijing Wang <wangyijing@xxxxxxxxxx>
> >> ---
> >>  drivers/pci/msi.c |    2 --
> >>  1 files changed, 0 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> >> index f6cb317..d547f7f 100644
> >> --- a/drivers/pci/msi.c
> >> +++ b/drivers/pci/msi.c
> >> @@ -41,8 +41,6 @@ int __weak arch_setup_msi_irq(struct pci_dev *dev, 
> >> struct msi_desc *desc)
> >>    if (err < 0)
> >>            return err;
> >>  
> >> -  irq_set_chip_data(desc->irq, chip);
> >> -
> >>    return 0;
> >>  }
> >>  
> > 
> > arch_teardown_msi_irq() expects to find the msi_chip in the irq
> > chip_data field. As this means drivers don't have any reasonable other
> > possibility to stuff things into this field, I think it would make sense
> > to do the cleanup the other way around: keep the irq_set_chip_data
> > arch_setup_msi_irq() and rip it out of the individual drivers.
> 
> Hi Lucas, thanks for your review and comments!
> irq_set_chip_data() should not be placed in MSI core functions, because other 
> arch like x86,
> use irq_data->chip_data to stores irq_cfg. So how to set the chip_data is 
> arch dependent.
> And this series is mainly to use MSI chip framework in all platforms.
> Currently, only ARM platform MSI drivers use the chip_data to store msi_chip, 
> and the drivers call
> irq_set_chip_data() in their driver already. So I thought we should clean up 
> it in MSI core code.
> 
Okay I see your point, so the cleanup done this way is okay.

But then this still introduces a problem: arch_teardown_msi_irq()
expects to find the msi_chip in the chip_data field, which is okay for
all ARM PCI host drivers, but not for other arch MSI chips.

You fix this by completely removing arch_teardown_msi_irq() at the end
of the series, but this still has the potential to introduce issues for
other arches than ARM within the series. So this patch should include a
change to replace the line

struct msi_chip *chip = irq_get_chip_data(irq);

with something that doesn't rely on the msi_chip being in the irq
chip_data field.

Regards,
Lucas

-- 
Pengutronix e.K.             | Lucas Stach                 |
Industrial Linux Solutions   | http://www.pengutronix.de/  |


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