lkml.org 
[lkml]   [2015]   [Sep]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v3 3/6] PCI: generic: Quit clobbering our pci_ops.
On 09/23/2015 01:21 AM, Arnd Bergmann wrote:
> On Tuesday 22 September 2015 16:49:14 David Daney wrote:
>> From: David Daney <david.daney@cavium.com>
>>
>> The pci-host-generic driver keeps a global struct pci_ops which it
>> then patches with the .map_bus method appropriate for the bus device.
>> A problem arises when the driver is used for two different types of
>> bus devices, the .map_bus method for the last device probed clobbers
>> the method for all previous devices. The result, only the last bus
>> device probed has the proper .map_bus, and the others fail.
>>
>> Move the struct pci_ops into the bus specific structure, and
>> initialize it when the bus device is probed. Keep a copy of the
>> gen_pci_cfg_bus_ops structure, instead of a pointer to a global copy,
>
> This is a very useful change.
>
>> to future proof against the addition of bus specific elements to
>> struct pci_ops.
>
> but I don't like this part. We should just not have bus specific
> elements in pci_ops. We don't really have that here either, except
> that the gen_pci driver had a hack for reusing the same operations
> for things that are actually different.
>
> It's an established practice that anything named '*_operations' is
> meant to be constant and ideally defined as 'static const ... *_ops;'
> in the driver. We could try to enforce this better by marking
> bus->ops as 'const' and changing all the instances of this structure
> accordingly.
>
>> @@ -65,7 +65,11 @@ static void __iomem *gen_pci_map_cfg_bus_cam(struct pci_bus *bus,
>>
>> static struct gen_pci_cfg_bus_ops gen_pci_cfg_cam_bus_ops = {
>> .bus_shift = 16,
>> - .map_bus = gen_pci_map_cfg_bus_cam,
>> + .ops = {
>> + .map_bus = gen_pci_map_cfg_bus_cam,
>> + .read = pci_generic_config_read,
>> + .write = pci_generic_config_write,
>> + }
>> };
>
> So this is good. We could in theory unify the map_bus functions
> like this now:
>
> static void __iomem *gen_pci_map_cfg_bus(struct pci_bus *bus,
> unsigned int devfn,
> int where)
> {
> struct gen_pci *pci = bus->sysdata;
> struct gen_pci_cfg_bus_ops *ops;
> resource_size_t idx;
>
> ops = container_of(bus->ops, struct gen_pci_cfg_bus_ops, ops);
> idx = bus->number - pci->cfg.bus_range->start;
>
> return pci->cfg.win[idx] + ((devfn << ops->dev_shift) | where);
> }
>
> Not sure if that improves clarity or not, up to Will.
>
>> @@ -234,8 +237,7 @@ static int gen_pci_probe(struct platform_device *pdev)
>> }
>>
>> of_id = of_match_node(gen_pci_of_match, np);
>> - pci->cfg.ops = of_id->data;
>> + pci->cfg.ops = *(struct gen_pci_cfg_bus_ops *)of_id->data;
>
> This is the part that grabbed my attention, we should not do it like this.
>

I will consider changing this so that a structure copy is not used,
perhaps as you suggest above.

David Daney.


> Arnd
>



\
 
 \ /
  Last update: 2015-09-23 18:41    [W:0.069 / U:0.600 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site