[PATCH i-g-t] tools/intel_reg: Add --pci-slot option

[Kamil Konieczny <kamil.konieczny@linux.intel.com>]

From: Łukasz Łaguna <lukasz.laguna@intel.com>

Add device selection by PCI slot with new option

--pci-slot <domain>:<bus>:<device>[.<func>]

Example:

intel_reg dump --pci-slot 0000:01:00.0
intel_reg dump --pci-slot 0000:8c:00

This should help in multi-GPU scenario when someone uses two or
more discrete GPUs.

v1: address review comments from Jani (Kamil)

Cc: Ashutosh Dixit <ashutosh.dixit@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Zbigniew Kempczyński <zbigniew.kempczynski@intel.com>
Signed-off-by: Łukasz Łaguna <lukasz.laguna@intel.com>
Signed-off-by: Kamil Konieczny <kamil.konieczny@linux.intel.com>
---
This is a re-work of Lukasz Laguna patch from
https://patchwork.freedesktop.org/series/131155/
("tools/intel_reg: add possibility to select device")

Example usage on two dGPU:
sudo ./intel_reg --pci-slot 0000:8c:00.0 read 0x00138108
                                    (0x00138108): 0xf4e57b26
sudo ./intel_reg --pci-slot 0000:87:00.0 read 0x00138108
                                    (0x00138108): 0xf4162825

 man/intel_reg.rst |   5 ++-
 tools/intel_reg.c | 106 +++++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 103 insertions(+), 8 deletions(-)

diff --git a/man/intel_reg.rst b/man/intel_reg.rst
index 059d8834a..64e4fa57f 100644
--- a/man/intel_reg.rst
+++ b/man/intel_reg.rst
@@ -9,7 +9,7 @@ Intel graphics register multitool
 :Author: Jani Nikula <jani.nikula@intel.com>
 :Date: 2016-03-01
 :Version: |PACKAGE_STRING|
-:Copyright: 2015-2016 Intel Corporation
+:Copyright: 2015-2025 Intel Corporation
 :Manual section: |MANUAL_SECTION|
 :Manual group: |MANUAL_GROUP|
 
@@ -56,6 +56,9 @@ Some options are global, and some specific to commands.
     Pretend to be PCI ID DEVID. Useful with MMIO bar snapshots from other
     machines.
 
+--pci-slot <domain>:<bus>:<device>[.<func>]
+    Find Intel GPU by PCI slot. Useful with multi-GPU hardware.
+
 --spec=PATH
     Read register spec from directory or file specified by PATH; see REGISTER
     SPEC DEFINITIONS below for details. This option implies --decode.
diff --git a/tools/intel_reg.c b/tools/intel_reg.c
index bb1ab2889..45f8b3a94 100644
--- a/tools/intel_reg.c
+++ b/tools/intel_reg.c
@@ -39,6 +39,7 @@
 #include "intel_chipset.h"
 
 #include "intel_reg_spec.h"
+#include "igt_device_scan.h"
 
 
 #ifdef HAVE_SYS_IO_H
@@ -89,6 +90,13 @@ struct config {
 	int verbosity;
 };
 
+struct igt_pci_slot {
+	int domain;
+	int bus;
+	int dev;
+	int func;
+};
+
 /* port desc must have been set */
 static int set_reg_by_addr(struct config *config, struct reg *reg,
 			   uint32_t addr)
@@ -1019,6 +1027,11 @@ static const struct command commands[] = {
 		.description = "list all known register names",
 		.decode = true,
 	},
+	{
+		.name = "help",
+		.function = intel_reg_help,
+		.description = "show this help",
+	},
 };
 
 static int intel_reg_help(struct config *config, int argc, char *argv[])
@@ -1055,6 +1068,8 @@ static int intel_reg_help(struct config *config, int argc, char *argv[])
 	printf(" --devid=DEVID  Specify PCI device ID for --mmio=FILE\n");
 	printf(" --decode       Decode registers. Implied by commands that require it\n");
 	printf(" --all          Decode registers for all known platforms. Implies --decode\n");
+	printf(" --pci-slot     Decode registers for platform described by PCI slot\n"
+	       "		<domain>:<bus>:<device>[.<func>]\n");
 	printf(" --binary       Binary dump registers\n");
 	printf(" --verbose      Increase verbosity\n");
 	printf(" --quiet        Reduce verbosity\n");
@@ -1164,6 +1179,62 @@ builtin:
 	return config->regcount;
 }
 
+static int parse_pci_slot_name(struct igt_pci_slot *st, const char *slot_name)
+{
+	int i;
+
+	st->domain = 0;
+	st->bus = 0;
+	st->dev = 0;
+	st->func = 0;
+	i = sscanf(slot_name, "%x:%x:%x.%x", &st->domain, &st->bus, &st->dev, &st->func);
+
+	return i;
+}
+
+static bool is_graphics_card_valid(struct pci_device *pci_dev)
+{
+	if (!pci_dev) {
+		fprintf(stderr, "Graphics card not found\n");
+		return false;
+	}
+	if (pci_device_probe(pci_dev) != 0) {
+		fprintf(stderr, "Couldn't probe graphics card\n");
+		return false;
+	}
+	if (pci_dev->vendor_id != 0x8086) {
+		fprintf(stderr, "Graphics card is non-intel\n");
+		return false;
+	}
+	return true;
+}
+
+static bool find_dev_from_slot(struct pci_device **pci_dev, char *opt_slot)
+{
+	struct igt_pci_slot bdf;
+	bool ret;
+
+	if (parse_pci_slot_name(&bdf, opt_slot) < 3) {
+		fprintf(stderr, "Cannot decode PCI slot from '%s'\n", opt_slot);
+		return false;
+	}
+
+	if (pci_system_init() != 0) {
+		fprintf(stderr, "Couldn't initialize PCI system\n");
+		return false;
+	}
+
+	igt_devices_scan();
+	*pci_dev = pci_device_find_by_slot(bdf.domain, bdf.bus, bdf.dev, bdf.func);
+	ret = is_graphics_card_valid(*pci_dev);
+	igt_devices_free();
+
+	if (!ret)
+		fprintf(stderr, "Cannot find PCI card given by slot '%s'\n", opt_slot);
+
+	return ret;
+}
+
 enum opt {
 	OPT_UNKNOWN = '?',
 	OPT_END = -1,
@@ -1173,6 +1244,7 @@ enum opt {
 	OPT_POST,
 	OPT_DECODE,
 	OPT_ALL,
+	OPT_SLOT,
 	OPT_BINARY,
 	OPT_SPEC,
 	OPT_VERBOSE,
@@ -1182,8 +1254,9 @@ enum opt {
 
 int main(int argc, char *argv[])
 {
-	int ret, i, index;
+	int i, index;
 	char *endp;
+	char *opt_slot = NULL;
 	enum opt opt;
 	const struct command *command = NULL;
 	struct config config = {
@@ -1191,6 +1264,7 @@ int main(int argc, char *argv[])
 		.fd = -1,
 	};
 	bool help = false;
+	int ret = EXIT_FAILURE;
 
 	static struct option options[] = {
 		/* global options */
@@ -1208,6 +1282,7 @@ int main(int argc, char *argv[])
 		/* options specific to read, dump and decode */
 		{ "decode",	no_argument,		NULL,	OPT_DECODE },
 		{ "all",	no_argument,		NULL,	OPT_ALL },
+		{ "pci-slot",	required_argument,	NULL,	OPT_SLOT },
 		{ "binary",	no_argument,		NULL,	OPT_BINARY },
 		{ 0 }
 	};
@@ -1257,6 +1332,14 @@ int main(int argc, char *argv[])
 		case OPT_DECODE:
 			config.decode = true;
 			break;
+		case OPT_SLOT:
+			opt_slot = strdup(optarg);
+			if (!opt_slot) {
+				fprintf(stderr, "strdup: %s\n",
+					strerror(errno));
+				return EXIT_FAILURE;
+			}
+			break;
 		case OPT_BINARY:
 			config.binary = true;
 			break;
@@ -1298,7 +1381,14 @@ int main(int argc, char *argv[])
 			fprintf(stderr, "--devid without --mmio\n");
 			return EXIT_FAILURE;
 		}
-		config.pci_dev = intel_get_pci_device();
+
+		if (opt_slot) {
+			if (!find_dev_from_slot(&config.pci_dev, opt_slot))
+				return EXIT_FAILURE;
+		} else {
+			config.pci_dev = intel_get_pci_device();
+		}
+
 		config.devid = config.pci_dev->device_id;
 	}
 
@@ -1311,21 +1401,23 @@ int main(int argc, char *argv[])
 
 	if (!command) {
 		fprintf(stderr, "'%s' is not an intel-reg command\n", argv[0]);
-		return EXIT_FAILURE;
+		goto exit;
 	}
 
 	if (command->decode)
 		config.decode = true;
 
-	if (read_reg_spec(&config) < 0)
-		return EXIT_FAILURE;
-
-	ret = command->function(&config, argc, argv);
+	if (read_reg_spec(&config) >= 0)
+		ret = command->function(&config, argc, argv);
 
+exit:
 	free(config.mmiofile);
 
 	if (config.fd >= 0)
 		close(config.fd);
 
+	if (opt_slot)
+		free(opt_slot);
+
 	return ret;
 }
-- 
2.48.1