Re: [PATCH v3 4/5] misc: pci_endpoint_test: Remove global irq_type

[Niklas Cassel <cassel@kernel.org>]

On Mon, Feb 10, 2025 at 04:58:11PM +0900, Kunihiko Hayashi wrote:
> The global variable "irq_type" preserves the current value of
> ioctl(GET_IRQTYPE), however, it's enough to use test->irq_type.
> Remove the variable, and replace with test->irq_type.

I think the commit message is missing the biggest point.

ioctl(SET_IRQTYPE) sets test->irq_type.
PCITEST_WRITE/PCITEST_READ/PCITEST_COPY all use test->irq_type when
writing the PCI_ENDPOINT_TEST_IRQ_TYPE register in test_reg_bar.

The endpoint function driver (pci-epf-test) will look at
PCI_ENDPOINT_TEST_IRQ_TYPE register in test_reg_bar when determining
which type of IRQ it should raise.

This means that the kernel module parameter is basically useless,
since it is unused if anyone has called ioctl(SET_IRQTYPE).

Both the old pcitest.sh and the new pci_endpoint_test kselftest call
ioctl(SET_IRQTYPE), so in practice the irq_type kernel module parameter
is dead code.


> 
> The ioctl(GET_IRQTYPE) returns an error if test->irq_type has
> IRQ_TYPE_UNDEFINED.
> 
> Suggested-by: Niklas Cassel <cassel@kernel.org>
> Suggested-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
> ---
>  drivers/misc/pci_endpoint_test.c | 13 ++++---------
>  1 file changed, 4 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/misc/pci_endpoint_test.c b/drivers/misc/pci_endpoint_test.c
> index 6a0972e7674f..8d98cd18634d 100644
> --- a/drivers/misc/pci_endpoint_test.c
> +++ b/drivers/misc/pci_endpoint_test.c
> @@ -100,10 +100,6 @@ static bool no_msi;
>  module_param(no_msi, bool, 0444);
>  MODULE_PARM_DESC(no_msi, "Disable MSI interrupt in pci_endpoint_test");

Considering that you are removing the irq_type kernel module parameter,
it doesn't make sense to keep the no_msi kernel module parameter IMO.

The exact same argument for why we are removing irq_type, can be made for
no_msi.


Kind regards,
Niklas