[PATCH v2 2/4] hw/cxl: Use switch statements for read and write of cachemem registers

[Jonathan Cameron]

Establishing that only register accesses of size 4 and 8 can occur
using these functions requires looking at their callers. Make it
easier to see that by using switch statements.
Assertions are used to enforce that the register storage is of the
matching size, allowing fixed values to be used for divisors of
the array indices.

Suggested-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
v2: Use switch statements. Note we coudl have renamed registers to make
    the sizes visible as is true of some other cases, but that felt odd
    as this is the only size these registers can be, so why call it out.
    The asserts do the same job.
 hw/cxl/cxl-component-utils.c | 65 +++++++++++++++++++++++-------------
 1 file changed, 42 insertions(+), 23 deletions(-)

diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c
index f3bbf0fd13..7ef3ef2bd6 100644
--- a/hw/cxl/cxl-component-utils.c
+++ b/hw/cxl/cxl-component-utils.c
@@ -67,16 +67,24 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr 
offset,
     CXLComponentState *cxl_cstate = opaque;
     ComponentRegisters *cregs = &cxl_cstate->crb;
 
-    if (size == 8) {
+    switch (size) {
+    case 4:
+        if (cregs->special_ops && cregs->special_ops->read) {
+            return cregs->special_ops->read(cxl_cstate, offset, 4);
+        } else {
+            static_assert(sizeof(*cregs->cache_mem_registers) == 4);
+            return cregs->cache_mem_registers[offset / 4];
+        }
+    case 8:
         qemu_log_mask(LOG_UNIMP,
                       "CXL 8 byte cache mem registers not implemented\n");
         return 0;
-    }
-
-    if (cregs->special_ops && cregs->special_ops->read) {
-        return cregs->special_ops->read(cxl_cstate, offset, size);
-    } else {
-        return cregs->cache_mem_registers[offset / 
sizeof(*cregs->cache_mem_registers)];
+    default:
+        /*
+         * In line with specifiction limitaions on access sizes, this
+         * routine is not called with other sizes.
+         */
+        g_assert_not_reached();
     }
 }
 
@@ -117,25 +125,36 @@ static void cxl_cache_mem_write_reg(void *opaque, hwaddr 
offset, uint64_t value,
     ComponentRegisters *cregs = &cxl_cstate->crb;
     uint32_t mask;
 
-    if (size == 8) {
+    switch (size) {
+    case 4:
+        static_assert(sizeof(*cregs->cache_mem_regs_write_mask) == 4);
+        static_assert(sizeof(*cregs->cache_mem_registers) == 4);
+        mask = cregs->cache_mem_regs_write_mask[offset / 4];
+        value &= mask;
+        /* RO bits should remain constant. Done by reading existing value */
+        value |= ~mask & cregs->cache_mem_registers[offset / 4];
+        if (cregs->special_ops && cregs->special_ops->write) {
+            cregs->special_ops->write(cxl_cstate, offset, value, size);
+            return;
+        }
+
+        if (offset >= A_CXL_HDM_DECODER_CAPABILITY &&
+            offset <= A_CXL_HDM_DECODER3_TARGET_LIST_HI) {
+            dumb_hdm_handler(cxl_cstate, offset, value);
+        } else {
+            cregs->cache_mem_registers[offset / 4] = value;
+        }
+        return;
+    case 8:
         qemu_log_mask(LOG_UNIMP,
                       "CXL 8 byte cache mem registers not implemented\n");
         return;
-    }
-    mask = cregs->cache_mem_regs_write_mask[offset / 
sizeof(*cregs->cache_mem_regs_write_mask)];
-    value &= mask;
-    /* RO bits should remain constant. Done by reading existing value */
-    value |= ~mask & cregs->cache_mem_registers[offset / 
sizeof(*cregs->cache_mem_registers)];
-    if (cregs->special_ops && cregs->special_ops->write) {
-        cregs->special_ops->write(cxl_cstate, offset, value, size);
-        return;
-    }
-
-    if (offset >= A_CXL_HDM_DECODER_CAPABILITY &&
-        offset <= A_CXL_HDM_DECODER3_TARGET_LIST_HI) {
-        dumb_hdm_handler(cxl_cstate, offset, value);
-    } else {
-        cregs->cache_mem_registers[offset / 
sizeof(*cregs->cache_mem_registers)] = value;
+    default:
+        /*
+         * In line with specifiction limitaions on access sizes, this
+         * routine is not called with other sizes.
+         */
+        g_assert_not_reached();
     }
 }
 
-- 
2.39.2