[PATCH 5/6] edac, mce_amd_inj: Add README file

[Aravind Gopalakrishnan <Aravind.Gopalakrishnan@amd.com>]

Provides information about each file and the usages.

Signed-off-by: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@amd.com>
---
 drivers/edac/mce_amd_inj.c | 68 +++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 61 insertions(+), 7 deletions(-)

diff --git a/drivers/edac/mce_amd_inj.c b/drivers/edac/mce_amd_inj.c
index f1c1433..ca5b29f 100644
--- a/drivers/edac/mce_amd_inj.c
+++ b/drivers/edac/mce_amd_inj.c
@@ -291,17 +291,71 @@ MCE_INJECT_GET(bank);
 
 DEFINE_SIMPLE_ATTRIBUTE(bank_fops, inj_bank_get, inj_bank_set, "%llu\n");
 
+static const char readme_msg[] =
+	"\nDescription of the files and their usages:\n\n"
+	"status:  Set a value to be programmed into MCx_STATUS(bank)\n"
+	"\t The status bits provide insight into the type of\n"
+	"\t error that caused the MCE.\n\n"
+	"misc:	 Set value of MCx_MISC(bank)\n"
+	"\t misc register provides auxiliary info about the error. This\n"
+	"\t register is typically used for error thresholding purpose and\n"
+	"\t validity of the register is indicated by MCx_STATUS[MiscV]\n\n"
+	"addr:	 Error address value to be written to MCx_ADDR(bank)\n"
+	"\t This register is used to log address information associated\n"
+	"\t with the error.\n\n"
+	"Note:	 See respective BKDGs for the exact bit definitions of the\n"
+	"\t above registers as they mirror the MCi_[STATUS | MISC | ADDR]\n"
+	"\t hardware registers.\n\n"
+	"bank:	 Specify the bank you want to inject the error into.\n"
+	"\t The number of banks in a processor varies and is family/model\n"
+	"\t dependent. So, a sanity check performed while writing.\n"
+	"\t Writing to this file will trigger a #MC or APIC interrupts or\n"
+	"\t invoke the error decoder routines for AMD processors. The value\n"
+	"\t in 'flags' file decides which of above actions is triggered.\n\n"
+	"flags:	 Write to this file to speficy the error injection policy.\n"
+	"\t Allowed values:\n"
+	"\t\t\"sw\"  -	SW error injection, Only calls error decoder\n"
+	"\t\t\troutines to print error info in human readable format\n"
+	"\t\t\"hw\"  -	HW error injection, Forces a #MC,\n"
+	"\t\t\tcauses exception handler to handle the error\n"
+	"\t\t\tif UC or poll handler catches it if CE\n"
+	"\t\t\tWarning: Might cause system panic if MCx_STATUS[PCC]\n"
+	"\t\t\tis set. For debug purposes, consider setting\n"
+	"\t\t\t/<debugfs_mountpoint>/mce/fake_panic\n"
+	"\t\t\"dfr\" -	Trigger APIC interrupt for Deferred error\n"
+	"\t\t\tError is handled by deferred error apic handler if\n"
+	"\t\t\tfeature is present in HW.\n"
+	"\t\t\"thr\" -	Trigger APIC interrupt for threshold error\n"
+	"\t\t\tError is handled by threshold apic handler\n\n"
+	"cpu:	 The cpu to inject the error on.\n\n"
+;
+
+static ssize_t
+inj_readme_read(struct file *filp, char __user *ubuf,
+		       size_t cnt, loff_t *ppos)
+{
+	return simple_read_from_buffer(ubuf, cnt, ppos,
+					readme_msg, strlen(readme_msg));
+}
+
+static const struct file_operations readme_fops = {
+	.read		= inj_readme_read,
+};
+
 static struct dfs_node {
 	char *name;
 	struct dentry *d;
 	const struct file_operations *fops;
+	umode_t perm;
 } dfs_fls[] = {
-	{ .name = "status",	.fops = &status_fops },
-	{ .name = "misc",	.fops = &misc_fops },
-	{ .name = "addr",	.fops = &addr_fops },
-	{ .name = "bank",	.fops = &bank_fops },
-	{ .name = "flags",	.fops = &flags_fops },
-	{ .name = "cpu",	.fops = &extcpu_fops },
+	{ .name = "status",	.fops = &status_fops,	S_IRUSR | S_IWUSR },
+	{ .name = "misc",	.fops = &misc_fops,	S_IRUSR | S_IWUSR },
+	{ .name = "addr",	.fops = &addr_fops,	S_IRUSR | S_IWUSR },
+	{ .name = "bank",	.fops = &bank_fops,	S_IRUSR | S_IWUSR },
+	{ .name = "flags",	.fops = &flags_fops,	S_IRUSR | S_IWUSR },
+	{ .name = "cpu",	.fops = &extcpu_fops,	S_IRUSR | S_IWUSR },
+	{ .name = "README",	.fops = &readme_fops,	S_IRUSR | S_IRGRP |
+							S_IROTH },
 };
 
 static int __init init_mce_inject(void)
@@ -318,7 +372,7 @@ static int __init init_mce_inject(void)
 
 	for (i = 0; i < ARRAY_SIZE(dfs_fls); i++) {
 		dfs_fls[i].d = debugfs_create_file(dfs_fls[i].name,
-						    S_IRUSR | S_IWUSR,
+						    dfs_fls[i].perm,
 						    dfs_inj,
 						    &i_mce,
 						    dfs_fls[i].fops);
-- 
2.4.0