Re: [PATCH v2 3/7] of/irq: Break out msi-map lookup (again)

[Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>]

On 14/06/16 15:37, Will Deacon wrote:
> On Fri, Jun 03, 2016 at 06:15:38PM +0100, Robin Murphy wrote:
>> The PCI msi-map code is already doing double-duty translating IDs and
>> retrieving MSI parents, which unsurprisingly is the same functionality
>> we need for the identically-formatted PCI iommu-map property. Drag the
>> core parsing routine up yet another layer into the general OF-PCI code,
>> and further generalise it for either kind of lookup in either flavour
>> of map property.
>>
>> CC: Rob Herring <robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
>> CC: Frank Rowand <frowand.list-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
>> CC: Marc Zyngier <marc.zyngier-5wv7dgnIgG8@public.gmane.org>
>> Signed-off-by: Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>
>> ---
>>
>> v2: No change.
>>
>>   drivers/of/irq.c       |  70 ++-------------------------------
>>   drivers/of/of_pci.c    | 102 +++++++++++++++++++++++++++++++++++++++++++++++++
>>   include/linux/of_pci.h |   8 ++++
>>   3 files changed, 114 insertions(+), 66 deletions(-)
>
> [...]
>
>> diff --git a/drivers/of/of_pci.c b/drivers/of/of_pci.c
>> index 13f4fed38048..20bf5a0c57fd 100644
>> --- a/drivers/of/of_pci.c
>> +++ b/drivers/of/of_pci.c
>> @@ -306,3 +306,105 @@ struct msi_controller *of_pci_find_msi_chip_by_node(struct device_node *of_node)
>>   EXPORT_SYMBOL_GPL(of_pci_find_msi_chip_by_node);
>>
>>   #endif /* CONFIG_PCI_MSI */
>> +
>> +#define MASK_NAME_LEN	32	/* Safely longer than "iommu-map-mask" */
>> +
>> +/**
>> + * of_pci_map_rid - Translate a requester ID through a downstream mapping.
>> + * @np: root complex device node.
>> + * @map_name: property name of the map to use.
>> + * @target: optional pointer to a target device node.
>> + * @id_out: optional pointer to receive the translated ID.
>> + *
>> + * Given a PCI requester ID, look up the appropriate implementation-defined
>> + * platform ID and/or the target device which receives transactions on that
>> + * ID, as per the "iommu-map" and "msi-map" bindings. @target or @id_out may
>> + * be NULL if not required. If @target points to a device node pointer, only
>> + * entries targeting that node will be matched; if it points to a NULL
>> + * value, it will receive the device node for the first matching target entry,
>> + * with a reference held.
>> + *
>> + * Return: 0 on success or a standard error code on failure.
>> + */
>> +int of_pci_map_rid(struct device_node *np, const char *map_name, u32 rid_in,
>> +		   struct device_node **target, u32 *rid_out)
>> +{
>> +	u32 map_mask, masked_rid;
>> +	int map_len;
>> +	const __be32 *map = NULL;
>> +	char mask_name[MASK_NAME_LEN];
>
> Couldn't you avoid this if you just took const char *mask_name as a
> parameter too?

Having started out with that, I considered two strings essentially 
duplicating each other, possibly duplicated per callsite, and thought it 
might be prudent to trade off a little runtime work for a permanent 
reduction in static data. I like the "never save anything you can 
recalculate" philosophy, but it is possible I got a bit carried away 
here. If you hate it I can just add the extra argument back.

Robin.

>
> Will
>