[PATCH] hw/input/tsc2005: Fix -Wchar-subscripts warning in tsc2005_txrx()

[Philippe Mathieu-Daudé]

Check the function index is not negative and use an unsigned
variable to avoid the following warning with GCC 13.2.0:

  [666/5358] Compiling C object libcommon.fa.p/hw_input_tsc2005.c.o
  hw/input/tsc2005.c: In function 'tsc2005_timer_tick':
  hw/input/tsc2005.c:416:26: warning: array subscript has type 'char' 
[-Wchar-subscripts]
    416 |     s->dav |= mode_regs[s->function];
        |                         ~^~~~~~~~~~

Signed-off-by: Philippe Mathieu-Daudé <phi...@linaro.org>
---
 hw/input/tsc2005.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/hw/input/tsc2005.c b/hw/input/tsc2005.c
index 941f163d36..fa93eb5d25 100644
--- a/hw/input/tsc2005.c
+++ b/hw/input/tsc2005.c
@@ -406,6 +406,7 @@ uint32_t tsc2005_txrx(void *opaque, uint32_t value, int len)
 static void tsc2005_timer_tick(void *opaque)
 {
     TSC2005State *s = opaque;
+    unsigned func_idx;
 
     /* Timer ticked -- a set of conversions has been finished.  */
 
@@ -413,7 +414,9 @@ static void tsc2005_timer_tick(void *opaque)
         return;
 
     s->busy = false;
-    s->dav |= mode_regs[s->function];
+    assert(s->function >= 0);
+    func_idx = s->function;
+    s->dav |= mode_regs[func_idx];
     s->function = -1;
     tsc2005_pin_update(s);
 }
-- 
2.41.0