[PATCH 2/2] selftests: ALSA: pcmtest: Make room for the longest fill pattern

[HyeongJun An]

The driver accepts fill patterns of up to 4096 bytes, as pcmtest.rst
documents. The test reads each pattern into a 1024-byte buffer, using
the length the driver reports. So a pattern longer than 1024 bytes
overflows the buffer into the next pattern and past the array.

Size the buffer to the driver's maximum.

Fixes: 10b98a4db11a ("selftests: ALSA: Add test for the 'pcmtest' driver")
Assisted-by: Claude:claude-opus-5-5
Signed-off-by: HyeongJun An <sammiee5...@gmail.com>
---
 tools/testing/selftests/alsa/test-pcmtest-driver.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/alsa/test-pcmtest-driver.c 
b/tools/testing/selftests/alsa/test-pcmtest-driver.c
index 5bba17434a6b..e025a7bac26b 100644
--- a/tools/testing/selftests/alsa/test-pcmtest-driver.c
+++ b/tools/testing/selftests/alsa/test-pcmtest-driver.c
@@ -10,9 +10,11 @@
 #include "kselftest_harness.h"
 
 #define CH_NUM 4
+/* The driver accepts patterns of up to 4096 bytes */
+#define MAX_PATTERN_LEN 4096
 
 struct pattern_buf {
-       char buf[1024];
+       char buf[MAX_PATTERN_LEN];
        int len;
 };
 
-- 
2.43.0