On Mon, Jul 1, 2013 at 7:42 AM, Thomas Petazzoni
<thomas.petazzoni@xxxxxxxxxxxxxxxxxx> wrote:
> From: Thierry Reding <thierry.reding@xxxxxxxxxxxxxxxxx>
>
> The new struct msi_chip is used to associated an MSI controller with a
> PCI bus. It is automatically handed down from the root to its children
> during bus enumeration.
>
> This patch provides default (weak) implementations for the architecture-
> specific MSI functions (arch_setup_msi_irq(), arch_teardown_msi_irq()
> and arch_msi_check_device()) which check if a PCI device's bus has an
> attached MSI chip and forward the call appropriately.
>
> Signed-off-by: Thierry Reding <thierry.reding@xxxxxxxxxxxxxxxxx>
> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@xxxxxxxxxxxxxxxxxx>
I'm OK with this patch in principle, but I do have a couple comments below.
> ---
> drivers/pci/msi.c | 22 ++++++++++++++++++++++
> drivers/pci/probe.c | 1 +
> include/linux/msi.h | 11 +++++++++++
> include/linux/pci.h | 1 +
> 4 files changed, 35 insertions(+)
>
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index 289fbfd..62eb3d5 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -32,15 +32,37 @@ static int pci_msi_enable = 1;
>
> int __weak arch_setup_msi_irq(struct pci_dev *dev, struct msi_desc *desc)
> {
> + struct msi_chip *chip = dev->bus->msi;
> +
> + if (chip && chip->setup_irq) {
> + int err;
> +
> + err = chip->setup_irq(chip, dev, desc);
> + if (err < 0)
> + return err;
> +
> + irq_set_chip_data(desc->irq, chip);
> + return err;
> + }
> +
> return -EINVAL;
It's sub-optimal to indent the whole body of a function like this. I
think this is a bit more readable:
if (!chip || !chip->setup_irq)
return -EINVAL
err = chip->setup_irq(...);
...
return err;
The return value of ->setup_irq() (and hence of arch_setup_msi_irq())
is a bit unclear. Apparently it can return negative values (errors)
or positive values (not sure what they mean), or zero (again, not
sure). A comment would clear this up.
It might even be worth introducing a no-op chip with pointers to no-op
functions so we don't have to do these checks ("if (chip &&
chip->xxx)" everywhere. I'm not sure if there's a Linux consensus on
that -- certainly there are many examples of code that *does* make
these checks everywhere -- so I'll ack it either way.
> }
>
> void __weak arch_teardown_msi_irq(unsigned int irq)
> {
> + struct msi_chip *chip = irq_get_chip_data(irq);
> +
> + if (chip && chip->teardown_irq)
> + chip->teardown_irq(chip, irq);
> }
>
> int __weak arch_msi_check_device(struct pci_dev *dev, int nvec, int type)
> {
> + struct msi_chip *chip = dev->bus->msi;
> +
> + if (chip && chip->check_device)
> + return chip->check_device(chip, dev, nvec, type);
> +
These functions are poorly named. They give no clue what
"check_device" means. Are we checking that it exists, that it
supports some property, that it's enabled, ... ?
> return 0;
> }
>
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 70f10fa..c8591e4 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -634,6 +634,7 @@ static struct pci_bus *pci_alloc_child_bus(struct pci_bus *parent,
>
> child->parent = parent;
> child->ops = parent->ops;
> + child->msi = parent->msi;
> child->sysdata = parent->sysdata;
> child->bus_flags = parent->bus_flags;
>
> diff --git a/include/linux/msi.h b/include/linux/msi.h
> index c82ff8d..5b357d92 100644
> --- a/include/linux/msi.h
> +++ b/include/linux/msi.h
> @@ -63,4 +63,15 @@ void arch_restore_msi_irqs(struct pci_dev *dev, int irq);
>
> void default_teardown_msi_irqs(struct pci_dev *dev);
>
> +struct msi_chip {
> + struct module *owner;
> + struct device *dev;
> +
> + int (*setup_irq)(struct msi_chip *chip, struct pci_dev *dev,
> + struct msi_desc *desc);
> + void (*teardown_irq)(struct msi_chip *chip, unsigned int irq);
> + int (*check_device)(struct msi_chip *chip, struct pci_dev *dev,
> + int nvec, int type);
> +};
> +
> #endif /* LINUX_MSI_H */
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 3a24e4f..7ffc012 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -432,6 +432,7 @@ struct pci_bus {
> struct resource busn_res; /* bus numbers routed to this bus */
>
> struct pci_ops *ops; /* configuration access functions */
> + struct msi_chip *msi; /* MSI controller */
> void *sysdata; /* hook for sys-specific extension */
> struct proc_dir_entry *procdir; /* directory entry in /proc/bus/pci */
>
> --
> 1.8.1.2
>
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