[dpdk-dev] [RFC] PCI config access for drivers

[Stephen Hemminger <shemming@brocade.com>]

Some drivers need ability to access PCI config (for example for power
management). This adds an abstraction to do this; only implemented
on Linux, but should be possible on BSD.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>

--- a/lib/librte_eal/common/include/rte_pci.h	2014-06-24 09:20:05.651993525 -0700
+++ b/lib/librte_eal/common/include/rte_pci.h	2014-06-24 09:25:42.150616572 -0700
@@ -151,6 +151,7 @@ struct rte_pci_device {
 	const struct rte_pci_driver *driver;    /**< Associated driver */
 	uint16_t max_vfs;                       /**< sriov enable if not zero */
 	int numa_node;                          /**< NUMA node connection */
+	int config_fd;				/**< PCI config access */
 	struct rte_devargs *devargs;            /**< Device user arguments */
 };
 
@@ -298,6 +299,34 @@ void rte_eal_pci_register(struct rte_pci
  */
 void rte_eal_pci_unregister(struct rte_pci_driver *driver);
 
+/**
+ * Read PCI config space.
+ *
+ * @param device
+ *   A pointer to a rte_pci_device structure describing the device
+ *   to use
+ * @param buf
+ *   A data buffer where the bytes should be read into
+ * @param size
+ *   The length of the data buffer.
+ */
+int rte_eal_pci_read_config(const struct rte_pci_device *device,
+			    void *buf, size_t len, off_t offset);
+
+/**
+ * Write PCI config space.
+ *
+ * @param device
+ *   A pointer to a rte_pci_device structure describing the device
+ *   to use
+ * @param buf
+ *   A data buffer containing the bytes should be written
+ * @param size
+ *   The length of the data buffer.
+ */
+int rte_eal_pci_write_config(const struct rte_pci_device *device,
+			     const void *buf, size_t len, off_t offset);
+
 #ifdef __cplusplus
 }
 #endif
--- a/lib/librte_eal/linuxapp/eal/eal_pci.c	2014-06-24 09:20:05.651993525 -0700
+++ b/lib/librte_eal/linuxapp/eal/eal_pci.c	2014-06-24 09:20:05.651993525 -0700
@@ -219,6 +219,7 @@ pci_scan_one(const char *dirname, uint16
 	dev->addr.bus = bus;
 	dev->addr.devid = devid;
 	dev->addr.function = function;
+	dev->config_fd = -1;
 
 	/* get vendor id */
 	snprintf(filename, sizeof(filename), "%s/vendor", dirname);
@@ -578,6 +579,20 @@ rte_eal_pci_probe_one_driver(struct rte_
 	return 1;
 }
 
+/* Read PCI config space. */
+int rte_eal_pci_read_config(const struct rte_pci_device *device,
+			    void *buf, size_t len, off_t offset)
+{
+	return pread(device->config_fd, buf, len, offset);
+}
+
+/* Write PCI config space. */
+int rte_eal_pci_write_config(const struct rte_pci_device *device,
+			     const void *buf, size_t len, off_t offset)
+{
+	return pwrite(device->config_fd, buf, len, offset);
+}
+
 /* Init the PCI EAL subsystem */
 int
 rte_eal_pci_init(void)
--- a/lib/librte_eal/linuxapp/eal/eal_pci_uio.c	2014-06-24 08:35:31.832146544 -0700
+++ b/lib/librte_eal/linuxapp/eal/eal_pci_uio.c	2014-06-24 09:37:44.892296443 -0700
@@ -280,6 +280,7 @@ pci_uio_map_resource(struct rte_pci_devi
 	int i, j;
 	char dirname[PATH_MAX];
 	char devname[PATH_MAX]; /* contains the /dev/uioX */
+	char cfgname[PATH_MAX];
 	void *mapaddr;
 	int uio_num;
 	uint64_t phaddr;
@@ -326,11 +327,23 @@ pci_uio_map_resource(struct rte_pci_devi
 	snprintf(uio_res->path, sizeof(uio_res->path), "%s", devname);
 	memcpy(&uio_res->pci_addr, &dev->addr, sizeof(uio_res->pci_addr));
 
+	/* Open fd for access to PCI config */
+	snprintf(cfgname, sizeof(cfgname),
+		 "%s/device/config", dirname);
+	dev->config_fd = open(cfgname, O_RDWR);
+	if (dev->config_fd < 0) {
+		RTE_LOG(ERR, EAL, "%s(): cannot open %s: %s\n",
+			__func__, cfgname, strerror(errno));
+		rte_free(uio_res);
+		return -1;
+	}
+
 	/* collect info about device mappings */
 	nb_maps = pci_uio_get_mappings(dirname, uio_res->maps,
 				       RTE_DIM(uio_res->maps));
 	if (nb_maps < 0) {
 		rte_free(uio_res);
+		close(dev->config_fd);
 		return nb_maps;
 	}
 
@@ -379,6 +392,7 @@ pci_uio_map_resource(struct rte_pci_devi
 
 			if (fail) {
 				rte_free(uio_res);
+				close(dev->config_fd);
 				close(fd);
 				return -1;
 			}