[PATCH v2] hw/scsi/megasas: Silent GCC duplicated-cond warning

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

From: Philippe Mathieu-Daudé <philmd@redhat.com>

GCC9 is confused when building with CFLAG -O3:

  hw/scsi/megasas.c: In function ‘megasas_scsi_realize’:
  hw/scsi/megasas.c:2387:26: error: duplicated ‘if’ condition [-Werror=duplicated-cond]
   2387 |     } else if (s->fw_sge >= 128 - MFI_PASS_FRAME_SIZE) {
  hw/scsi/megasas.c:2385:19: note: previously used here
   2385 |     if (s->fw_sge >= MEGASAS_MAX_SGE - MFI_PASS_FRAME_SIZE) {
  cc1: all warnings being treated as errors

When this device was introduced in commit e8f943c3bcc, the author
cared about modularity, using a definition for the firmware limit.

However if the firmware limit isn't changed (MEGASAS_MAX_SGE = 128),
the code ends doing the same check twice.

Per the maintainer [*]:

> The original code assumed that one could change MFI_PASS_FRAME_SIZE,
> but it turned out not to be possible as it's being hardcoded in the
> drivers themselves (even though the interface provides mechanisms to
> query it). So we can remove the duplicate lines.

Add the 'MEGASAS_MIN_SGE' definition for the '64' magic value,
slightly rewrite the condition check to simplify a bit the logic
and remove the unnecessary / duplicated check.

[*] https://lore.kernel.org/qemu-devel/e0029fc5-882f-1d63-15e3-1c3dbe9b6a2c@suse.de/

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
v1: https://lore.kernel.org/qemu-devel/20191217173425.5082-6-philmd@redhat.com/
---
 hw/scsi/megasas.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/hw/scsi/megasas.c b/hw/scsi/megasas.c
index 9cbbb16121..32c70c9e99 100644
--- a/hw/scsi/megasas.c
+++ b/hw/scsi/megasas.c
@@ -42,6 +42,7 @@
 #define MEGASAS_MAX_FRAMES 2048         /* Firmware limit at 65535 */
 #define MEGASAS_DEFAULT_FRAMES 1000     /* Windows requires this */
 #define MEGASAS_GEN2_DEFAULT_FRAMES 1008     /* Windows requires this */
+#define MEGASAS_MIN_SGE 64
 #define MEGASAS_MAX_SGE 128             /* Firmware limit */
 #define MEGASAS_DEFAULT_SGE 80
 #define MEGASAS_MAX_SECTORS 0xFFFF      /* No real limit */
@@ -2356,6 +2357,7 @@ static void megasas_scsi_realize(PCIDevice *dev, Error **errp)
     MegasasState *s = MEGASAS(dev);
     MegasasBaseClass *b = MEGASAS_GET_CLASS(s);
     uint8_t *pci_conf;
+    uint32_t sge;
     int i, bar_type;
     Error *err = NULL;
     int ret;
@@ -2424,13 +2426,15 @@ static void megasas_scsi_realize(PCIDevice *dev, Error **errp)
     if (!s->hba_serial) {
         s->hba_serial = g_strdup(MEGASAS_HBA_SERIAL);
     }
-    if (s->fw_sge >= MEGASAS_MAX_SGE - MFI_PASS_FRAME_SIZE) {
-        s->fw_sge = MEGASAS_MAX_SGE - MFI_PASS_FRAME_SIZE;
-    } else if (s->fw_sge >= 128 - MFI_PASS_FRAME_SIZE) {
-        s->fw_sge = 128 - MFI_PASS_FRAME_SIZE;
-    } else {
-        s->fw_sge = 64 - MFI_PASS_FRAME_SIZE;
+
+    sge = s->fw_sge + MFI_PASS_FRAME_SIZE;
+    if (sge < MEGASAS_MIN_SGE) {
+        sge = MEGASAS_MIN_SGE;
+    } else if (sge >= MEGASAS_MAX_SGE) {
+        sge = MEGASAS_MAX_SGE;
     }
+    s->fw_sge = sge - MFI_PASS_FRAME_SIZE;
+
     if (s->fw_cmds > MEGASAS_MAX_FRAMES) {
         s->fw_cmds = MEGASAS_MAX_FRAMES;
     }
-- 
2.38.1