linux-kernel - [PATCH v4 2/3] efi/cper: Add a new helper function to print bitmasks

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Message-ID: <fcc8a699c9497b788ac99aa0d57dedd629ac4945.1718906288.git.mchehab+huawei@kernel.org>
Date: Thu, 20 Jun 2024 20:01:45 +0200
From: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
To: 
Cc: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
	"Borislav Petkov" <bp@...en8.de>,
	"James Morse" <james.morse@....com>,
	"Jonathan Cameron" <Jonathan.Cameron@...wei.com>,
	"Shiju Jose" <shiju.jose@...wei.com>,
	"Tony Luck" <tony.luck@...el.com>,
	Ard Biesheuvel <ardb@...nel.org>,
	Dave Jiang <dave.jiang@...el.com>,
	Ira Weiny <ira.weiny@...el.com>,
	linux-edac@...r.kernel.org,
	linux-efi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v4 2/3] efi/cper: Add a new helper function to print bitmasks

Sometimes it is desired to produce a single log line for errors.
Add a new helper function for such purpose.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
---
 drivers/firmware/efi/cper.c | 59 +++++++++++++++++++++++++++++++++++++
 include/linux/cper.h        |  3 ++
 2 files changed, 62 insertions(+)

diff --git a/drivers/firmware/efi/cper.c b/drivers/firmware/efi/cper.c
index 7d2cdd9e2227..9bf27af3e870 100644
--- a/drivers/firmware/efi/cper.c
+++ b/drivers/firmware/efi/cper.c
@@ -106,6 +106,65 @@ void cper_print_bits(const char *pfx, unsigned int bits,
 		printk("%s\n", buf);
 }
 
+/*
+ * cper_bits_to_str - return a string for set bits
+ * @buf: buffer to store the output string
+ * @buf_size: size of the output string buffer
+ * @bits: bit mask
+ * @strs: string array, indexed by bit position
+ * @strs_size: size of the string array: @strs
+ *
+ * add to @buf the bitmask in hexadecimal. Then, for each set bit in @bits,
+ * add the corresponding string in @strs to @buf.
+ */
+char *cper_bits_to_str(char *buf, int buf_size, unsigned int bits,
+		       const char * const strs[], unsigned int strs_size,
+		       unsigned int mask)
+{
+	int i, size, first_bit;
+	int len = buf_size;
+	const char *start;
+	char *str = buf;
+
+	if (strs_size < 16)
+		size = snprintf(str, len, "0x%02x: ", bits);
+	if (strs_size < 32)
+		size = snprintf(str, len, "0x%04x: ", bits);
+
+	len -= size;
+	str += size;
+
+	start = str;
+
+	if (mask) {
+		first_bit = ffs(mask) - 1;
+		if (bits & ~mask) {
+			size = strscpy(str, "reserved bit(s)", len);
+			len -= size;
+			str += size;
+		}
+	} else {
+		first_bit = 0;
+	}
+
+	for (i = 0; i < strs_size; i++) {
+		if (!(bits & (1U << (i + first_bit))))
+			continue;
+
+		if (*start && len > 0) {
+			*str = '|';
+			len--;
+			str++;
+		}
+
+		size = strscpy(str, strs[i], len);
+		len -= size;
+		str += size;
+	}
+	return buf;
+}
+EXPORT_SYMBOL_GPL(cper_bits_to_str);
+
 static const char * const proc_type_strs[] = {
 	"IA32/X64",
 	"IA64",
diff --git a/include/linux/cper.h b/include/linux/cper.h
index 265b0f8fc0b3..856e8f00a7fb 100644
--- a/include/linux/cper.h
+++ b/include/linux/cper.h
@@ -584,6 +584,9 @@ const char *cper_mem_err_type_str(unsigned int);
 const char *cper_mem_err_status_str(u64 status);
 void cper_print_bits(const char *prefix, unsigned int bits,
 		     const char * const strs[], unsigned int strs_size);
+char *cper_bits_to_str(char *buf, int buf_size, unsigned int bits,
+		       const char * const strs[], unsigned int strs_size,
+		       unsigned int mask);
 void cper_mem_err_pack(const struct cper_sec_mem_err *,
 		       struct cper_mem_err_compact *);
 const char *cper_mem_err_unpack(struct trace_seq *,
-- 
2.45.2