fw_cfg: add generic non-DMA read method
Introduce fw_cfg_data_read(), a generic read method which works
on all access widths (1 through 8 bytes, inclusive), and can be
used during both IOPort and MMIO read accesses.
To maintain legibility, only fw_cfg_data_mem_read() (the MMIO
data read method) is replaced by this patch. The new method
essentially unwinds the fw_cfg_data_mem_read() + fw_cfg_read()
combo, but without unnecessarily repeating all the validity
checks performed by the latter on each byte being read.
This patch also modifies the trace_fw_cfg_read prototype to
accept a 64-bit value argument, allowing it to work properly
with the new read method, but also remain backward compatible
with existing call sites.
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Marc Marí <markmb@redhat.com>
Signed-off-by: Gabriel Somlo <somlo@cmu.edu>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Message-id: 1446733972-1602-6-git-send-email-somlo@cmu.edu
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
index 046fa74..8f566f6 100644
--- a/hw/nvram/fw_cfg.c
+++ b/hw/nvram/fw_cfg.c
@@ -274,6 +274,36 @@
return ret;
}
+static uint64_t fw_cfg_data_read(void *opaque, hwaddr addr, unsigned size)
+{
+ FWCfgState *s = opaque;
+ int arch = !!(s->cur_entry & FW_CFG_ARCH_LOCAL);
+ FWCfgEntry *e = (s->cur_entry == FW_CFG_INVALID) ? NULL :
+ &s->entries[arch][s->cur_entry & FW_CFG_ENTRY_MASK];
+ uint64_t value = 0;
+
+ assert(size > 0 && size <= sizeof(value));
+ if (s->cur_entry != FW_CFG_INVALID && e->data && s->cur_offset < e->len) {
+ /* The least significant 'size' bytes of the return value are
+ * expected to contain a string preserving portion of the item
+ * data, padded with zeros on the right in case we run out early.
+ * In technical terms, we're composing the host-endian representation
+ * of the big endian interpretation of the fw_cfg string.
+ */
+ do {
+ value = (value << 8) | e->data[s->cur_offset++];
+ } while (--size && s->cur_offset < e->len);
+ /* If size is still not zero, we *did* run out early, so continue
+ * left-shifting, to add the appropriate number of padding zeros
+ * on the right.
+ */
+ value <<= 8 * size;
+ }
+
+ trace_fw_cfg_read(s, value);
+ return value;
+}
+
static uint8_t fw_cfg_read(FWCfgState *s)
{
int arch = !!(s->cur_entry & FW_CFG_ARCH_LOCAL);
@@ -291,19 +321,6 @@
return ret;
}
-static uint64_t fw_cfg_data_mem_read(void *opaque, hwaddr addr,
- unsigned size)
-{
- FWCfgState *s = opaque;
- uint64_t value = 0;
- unsigned i;
-
- for (i = 0; i < size; ++i) {
- value = (value << 8) | fw_cfg_read(s);
- }
- return value;
-}
-
static void fw_cfg_data_mem_write(void *opaque, hwaddr addr,
uint64_t value, unsigned size)
{
@@ -485,7 +502,7 @@
};
static const MemoryRegionOps fw_cfg_data_mem_ops = {
- .read = fw_cfg_data_mem_read,
+ .read = fw_cfg_data_read,
.write = fw_cfg_data_mem_write,
.endianness = DEVICE_BIG_ENDIAN,
.valid = {
diff --git a/trace-events b/trace-events
index 2fce98e..7fc4d11 100644
--- a/trace-events
+++ b/trace-events
@@ -196,7 +196,7 @@
# hw/nvram/fw_cfg.c
fw_cfg_select(void *s, uint16_t key, int ret) "%p key %d = %d"
-fw_cfg_read(void *s, uint8_t ret) "%p = %d"
+fw_cfg_read(void *s, uint64_t ret) "%p = %"PRIx64
fw_cfg_add_file(void *s, int index, char *name, size_t len) "%p #%d: %s (%zd bytes)"
# hw/block/hd-geometry.c
