Re: [dpdk-dev] [PATCH 1/4] pci: allow access to PCI config space

[Stephen Hemminger <stephen@networkplumber.org>]

Here is a revised version that works for both UIO and VFIO.
The config access is property of device not the I/O model.

From: Stephen Hemminger <stephen@networkplumber.org>
Subject: [PATCH 1/4] pci: allow access to PCI config space

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>
---
 lib/librte_eal/common/include/rte_pci.h   | 29 +++++++++++++++++++++++++++++
 lib/librte_eal/linuxapp/eal/eal_pci.c     | 15 +++++++++++++++
 lib/librte_eal/linuxapp/eal/eal_pci_uio.c | 10 ++++++++++
 3 files changed, 54 insertions(+)

Index: dpdk/lib/librte_eal/common/include/rte_pci.h
===================================================================
--- dpdk.orig/lib/librte_eal/common/include/rte_pci.h	2015-02-10 15:58:53.915744256 -0800
+++ dpdk/lib/librte_eal/common/include/rte_pci.h	2015-02-10 15:58:53.911744221 -0800
@@ -152,6 +152,7 @@
 	uint16_t max_vfs;                       /**< sriov enable if not zero */
 	int numa_node;                          /**< NUMA node connection */
 	struct rte_devargs *devargs;            /**< Device user arguments */
+	int config_fd;				/**< PCI config access */
 };
 
 /** Any PCI device identifier (vendor, device, ...) */
@@ -304,6 +305,34 @@
  */
 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
Index: dpdk/lib/librte_eal/linuxapp/eal/eal_pci.c
===================================================================
--- dpdk.orig/lib/librte_eal/linuxapp/eal/eal_pci.c	2015-02-10 15:58:53.915744256 -0800
+++ dpdk/lib/librte_eal/linuxapp/eal/eal_pci.c	2015-02-10 15:59:46.564201569 -0800
@@ -34,6 +34,7 @@
 #include <string.h>
 #include <dirent.h>
 #include <sys/mman.h>
+#include <sys/fcntl.h>
 
 #include <rte_log.h>
 #include <rte_pci.h>
@@ -233,6 +234,7 @@
 	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);
@@ -498,6 +500,26 @@
 #endif
 
 static int
+pci_config_open(struct rte_pci_device *dev)
+{
+	struct rte_pci_addr *loc = &dev->addr;
+	char filename[PATH_MAX];
+
+	/* Open fd for access to PCI config */
+	snprintf(filename, sizeof(filename),
+		 SYSFS_PCI_DEVICES "/" PCI_PRI_FMT "/config",
+		 loc->domain, loc->bus, loc->devid, loc->function);
+	dev->config_fd = open(filename, O_RDWR);
+	if (dev->config_fd < 0) {
+		RTE_LOG(ERR, EAL, "%s(): cannot open %s: %s\n",
+			__func__, filename, strerror(errno));
+		return -1;
+	}
+
+	return 0;
+}
+
+static int
 pci_map_device(struct rte_pci_device *dev)
 {
 	int ret, mapped = 0;
@@ -518,7 +540,8 @@
 		if (ret != 0)
 			return ret;
 	}
-	return 0;
+
+	return pci_config_open(dev);
 }
 
 /*
@@ -595,6 +618,20 @@
 	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)