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

[Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>]

On Tue, Jun 14, 2016 at 07:12:46PM +0100, Robin Murphy wrote:
> 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.

Yeah, please do. The idea is that this can be used with different bindings,
and I don't think we gain anything from constructing the mask string other
than and ugliness complexity.

Will
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