[v2,1/2] console/serial: set the default transmit buffer size in Kconfig

Commit Message

Roger Pau Monne June 30, 2022, 8:23 a.m. UTC

Take the opportunity to convert the variable to read-only after init.

No functional change intended.

Signed-off-by: Roger Pau Monné <[e-mail]>
---
Changes since v1:
 - Fix help message about rounded boundary, do not round up the
   default value (will be done at runtime).
 - Use kiB instead of KB.
---
 xen/drivers/char/Kconfig  | 10 ++++++++++
 xen/drivers/char/serial.c |  2 +-
 2 files changed, 11 insertions(+), 1 deletion(-)

Comments

Jan Beulich June 30, 2022, 8:52 a.m. UTC | #1

On 30.06.2022 10:23, Roger Pau Monne wrote:
> Take the opportunity to convert the variable to read-only after init.
> 
> No functional change intended.
> 
> Signed-off-by: Roger Pau Monné <[e-mail]>

Reviewed-by: Jan Beulich <[e-mail]>

Patch

diff --git a/xen/drivers/char/Kconfig b/xen/drivers/char/Kconfig
index e5f7b1d8eb..dec58bc993 100644
--- a/xen/drivers/char/Kconfig
+++ b/xen/drivers/char/Kconfig
@@ -74,3 +74,13 @@  config HAS_EHCI
 	help
 	  This selects the USB based EHCI debug port to be used as a UART. If
 	  you have an x86 based system with USB, say Y.
+
+config SERIAL_TX_BUFSIZE
+	int "Size of the transmit serial buffer"
+	default 16384
+	help
+	  Controls the default size of the transmit buffer (in bytes) used by
+	  the serial driver.  Note the value provided will be rounded down to
+	  the nearest power of 2.
+
+	  Default value is 16384 (16kiB).
diff --git a/xen/drivers/char/serial.c b/xen/drivers/char/serial.c
index 5ecba0af33..f6c944bd30 100644
--- a/xen/drivers/char/serial.c
+++ b/xen/drivers/char/serial.c
@@ -16,7 +16,7 @@ 
 /* Never drop characters, even if the async transmit buffer fills. */
 /* #define SERIAL_NEVER_DROP_CHARS 1 */
 
-unsigned int __read_mostly serial_txbufsz = 16384;
+unsigned int __ro_after_init serial_txbufsz = CONFIG_SERIAL_TX_BUFSIZE;
 size_param("serial_tx_buffer", serial_txbufsz);
 
 #define mask_serial_rxbuf_idx(_i) ((_i)&(serial_rxbufsz-1))