[PATCH 4/4] arm64: advertise CPU features for modalias matching

[Ard Biesheuvel]

This enables the generic implementation in drivers/base/cpu.c
that allows modules to be loaded automatically based on the
optional features supported (and advertised over udev) by the
CPU.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
---
 arch/arm64/Kconfig        |  3 +++
 arch/arm64/kernel/setup.c | 20 ++++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index c044548..50cd97f 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -202,6 +202,9 @@ config ARCH_WANT_HUGE_PMD_SHARE
 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 	def_bool y
 
+config ARCH_HAS_CPU_AUTOPROBE
+	def_bool y
+
 source "mm/Kconfig"
 
 config XEN_DOM0
diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index 780a7aa..4774304 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -403,3 +403,23 @@ const struct seq_operations cpuinfo_op = {
 	.stop	= c_stop,
 	.show	= c_show
 };
+
+ssize_t arch_print_cpu_modalias(struct device *dev,
+				struct device_attribute *attr,
+				char *buf)
+{
+	unsigned int caps;
+	ssize_t n;
+	int i;
+
+	/*
+	 * With 32 features maximum (taking 5 bytes each to print), we don't
+	 * need to worry about overrunning the PAGE_SIZE sized buffer.
+	 */
+	n = sprintf(buf, "cpu:type:arm64:feature:");
+	for (caps = elf_hwcap, i = 0; caps; caps >>= 1, i++)
+		if (caps & 1)
+			n += sprintf(&buf[n], ",%04X", i);
+	buf[n++] = '\n';
+	return n;
+}
-- 
1.8.3.2

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