linux-kernel - Re: [PATCH] PCI: add kernel parameter to override devid<->driver mapping.

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Message-ID: <1413116386.6042.13.camel@localhost.localdomain>
Date:	Sun, 12 Oct 2014 15:19:46 +0300
From:	Marcel Apfelbaum <marcel.a@...hat.com>
To:	Alex Williamson <alex.williamson@...hat.com>
Cc:	linux-pci@...r.kernel.org, bhelgaas@...gle.com,
	linux-kernel@...r.kernel.org, marcel@...hat.com, mst@...hat.com
Subject: Re: [PATCH] PCI: add kernel parameter to override devid<->driver
 mapping.

On Wed, 2014-10-01 at 12:48 -0600, Alex Williamson wrote:
> On Tue, 2014-09-30 at 19:38 +0300, Marcel Apfelbaum wrote:
> > Scanning a lot of devices during boot requires a lot of time.
> > On other scenarios there is a need to bind a driver to a specific slot.
> > 
> > Binding devices to pci-stub driver does not work,
> > as it will not differentiate between devices of the
> > same type. Using some start scripts is error prone.
> > 
> > The solution leverages driver_override functionality introduced by
> > 
> > 	commit: 782a985d7af26db39e86070d28f987cad21313c0
> > 	Author: Alex Williamson <alex.williamson@...hat.com>
> > 	Date:   Tue May 20 08:53:21 2014 -0600
> > 
> >     	PCI: Introduce new device binding path using pci_dev.driver_override
> > 
> > In order to bind PCI slot 0001:02:03.4 to pci-stub use:
> > 	driver[0001:02:03.4]=pci-stub
> 
> So the option is actually:
> 
> pci=driver=[...]=foo,driver=[...]=bar
> 
> That's not very clear from the commit log.
> 

[...]
Hi Alex,
I am sorry, but I missed the bellow comments, I am going to
fix them for the next version.

> > +
> > +struct driver_override_entry {
> > +	unsigned int domain;
> 
> u16
Sure
> 
> > +	unsigned char bus;
> 
> u8
Sure
> 
> > +	unsigned int devfn;
> 
> u8
Sure
> 
> > +	char driver_name[DRIVER_OVERRIDE_NAME_LENGTH];
I'll allocate it dynamically

> > +};
> > +
> > +static struct driver_override_entry __initdata
> > +	driver_override_map[DRIVER_OVERRIDE_MAP_SIZE];
> > +static int driver_override_num_entries __initdata;
> > +
> > +void pci_device_setup_driver_override(struct pci_dev *dev)
> > +{
> > +	int i;
> > +
> > +	for (i = 0; i < driver_override_num_entries; i++) {
> > +		if (pci_domain_nr(dev->bus) != driver_override_map[i].domain ||
> > +		    dev->bus->number != driver_override_map[i].bus ||
> > +		    dev->devfn != driver_override_map[i].devfn)
> > +			continue;
> > +
> > +		dev->driver_override = kstrndup(driver_override_map[i].driver_name,
> > +						DRIVER_OVERRIDE_NAME_LENGTH,
> > +						GFP_KERNEL);
> > +		break;
> > +	}
> > +}
> > +
> > +static void __init pci_parse_driver_override(char *str)
> > +{
> > +	unsigned int domain, bus, dev, fn;
> > +	char driver_name[DRIVER_OVERRIDE_NAME_LENGTH];
> > +	int ret, next_entry;
> > +	char format[] = "[%4x:%2x:%2x.%2x]=%%%ds";
> > +
> > +	sprintf(format + 18, "%%%ds", DRIVER_OVERRIDE_NAME_LENGTH);
> 
> There must be a less confusing way to do this.
I'll try it, and also I'll get rid of DRIVER_OVERRIDE_NAME_LENGTH
restriction.

> 
> > +	ret = sscanf(str, format, &domain, &bus, &dev, &fn, driver_name);
> > +
> > +	if (ret != 5) {
> > +		pr_err("PCI: Invalid command line: driver%s\n", str);
> > +		return;
> > +	}
> > +
> > +	if (driver_override_num_entries == DRIVER_OVERRIDE_MAP_SIZE) {
> > +		pr_err("PCI: Driver map overflow - ignoring driver%s\n", str);
> > +		return;
> > +	}
> > +
> > +	next_entry = driver_override_num_entries++;
> > +	driver_override_map[next_entry].domain = domain;
> > +	driver_override_map[next_entry].bus = bus && 0xff;
> 
> How could it not be given our format?
Right, I'll remove the check.
> 
> > +	driver_override_map[next_entry].devfn = ((dev & 0x1f) << 3) | (fn & 0x7);
> 
> PCI_DEVFN(dev, fn)
Sure,

Thank you for the review,
Marcel

> 
> > +	memcpy(driver_override_map[next_entry].driver_name,
> > +	       driver_name, sizeof(driver_name));
> > +}
> > +
> >  static int __init pci_setup(char *str)
> >  {
> >  	while (str) {
> > @@ -4468,6 +4527,8 @@ static int __init pci_setup(char *str)
> >  				pcie_bus_config = PCIE_BUS_PEER2PEER;
> >  			} else if (!strncmp(str, "pcie_scan_all", 13)) {
> >  				pci_add_flags(PCI_SCAN_ALL_PCIE_DEVS);
> > +			} else if (!strncmp(str, "driver", 6)) {
> > +				pci_parse_driver_override(str + 6);
> >  			} else {
> >  				printk(KERN_ERR "PCI: Unknown option `%s'\n",
> >  						str);
> > diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> > index 0601890..023d78b 100644
> > --- a/drivers/pci/pci.h
> > +++ b/drivers/pci/pci.h
> > @@ -197,6 +197,7 @@ enum pci_bar_type {
> >  bool pci_bus_read_dev_vendor_id(struct pci_bus *bus, int devfn, u32 *pl,
> >  				int crs_timeout);
> >  int pci_setup_device(struct pci_dev *dev);
> > +void pci_device_setup_driver_override(struct pci_dev *dev);
> >  int __pci_read_base(struct pci_dev *dev, enum pci_bar_type type,
> >  		    struct resource *res, unsigned int reg);
> >  int pci_resource_bar(struct pci_dev *dev, int resno, enum pci_bar_type *type);
> 
> 
> 



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