Differences

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--- devm_ioremap_resource [2018/07/30 16:40] – [Broadcom Cygnus] rpjday
+++ devm_ioremap_resource [2018/07/31 11:59] (current) – [platform_get_resource()] rpjday
@@ Line 1: / Line 1: @@
 ===== Overview =====
-Explain ''devm_ioremap_resource()'', with examples. Add some links.
+Explain ''devm_ioremap_resource()'', with examples particularly related to memory regions. Add some links.
-===== Let's talk about resources =====
+===== struct resource =====
-==== struct resource ====
 From ''include/linux/ioport.h'', a device can have a number of resources of different types:
@@ Line 24: / Line 22: @@
 </code>
+In particular, one resource type is a memory range (''flags'' of ''IORESOURCE_MEM''):
-A small sample of resource types from that same file (''IORESOURCE_MEM'' is the one representing physical memory that many drivers are interested in):
 <code>
@@ Line 40: / Line 37: @@
 </code>
-==== struct platform_device ====
+Here's a single example from ''arch/arm/mach-davinci/dm355.c'', defining an array of resources:
-From ''include/linux/platform_device.h'':
+<code>
+static struct resource edma_resources[] = {
+        {
+                .name   = "edma3_cc",
+                .start  = 0x01c00000,
+                .end    = 0x01c00000 + SZ_64K - 1,
+                .flags  = IORESOURCE_MEM,
+        },
+        {
+                .name   = "edma3_tc0",
+                .start  = 0x01c10000,
+                .end    = 0x01c10000 + SZ_1K - 1,
+                .flags  = IORESOURCE_MEM,
+        },
+        {
+                .name   = "edma3_tc1",
+                .start  = 0x01c10400,
+                .end    = 0x01c10400 + SZ_1K - 1,
+                .flags  = IORESOURCE_MEM,
+        },
+        ... snip ...
+</code>
+===== struct platform_device =====
+From ''include/linux/platform_device.h'', showing how a ''platform_device'' can represent any number of resources:
 <code>
@@ Line 72: / Line 93: @@
 ===== platform_get_resource() =====
-From ''drivers/base/platform.c'', given a platform device and a resource type, return that resource type or ''NULL'':
+From ''drivers/base/platform.c'', given a ''struct platform_device *dev'' and a resource type, return that (numbered) resource type or ''NULL'':
 <code>
@@ Line 95: / Line 116: @@
 	return NULL;
 }
+</code>
+You can also get a resource by an optional name:
+<code>
+/**
+ * platform_get_resource_byname - get a resource for a device by name
+ * @dev: platform device
+ * @type: resource type
+ * @name: resource name
+ */
+struct resource *platform_get_resource_byname(struct platform_device *dev,
+                                              unsigned int type,
+                                              const char *name)
+{
+        int i;
+        for (i = 0; i < dev->num_resources; i++) {
+                struct resource *r = &dev->resource[i];
+                if (unlikely(!r->name))
+                        continue;
+                if (type == resource_type(r) && !strcmp(r->name, name))
+                        return r;
+        }
 </code>