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authorPeter Oberparleiter <oberpar@linux.ibm.com>2021-03-02 17:28:12 +0100
committerHeiko Carstens <hca@linux.ibm.com>2021-03-22 11:36:03 +0100
commit98ce70b76942626fc36c1a972fe1c5a303ac716d (patch)
tree857f1e2d6764d8cf8b1174e2e3642259c16f14bd
parent37564ed834aca26993b77b9b2a0119ec1ba6e00c (diff)
s390/sclp: increase sclp console line length
Kernel and console/TTY messages written to the SCLP line mode console are wrapped at 80 characters per line by the associated SCLP driver. This makes long lines of output difficult to read, and requires editing of wrapped lines copied from the output device. Neither the firmware interface used to access the SCLP console, nor the HMC "Operating System Messages" web interface that displays these messages require such a length limit. Also other operating systems such as z/VM do not impose similar limits on messages they emit to the same console device. This patch therefore increases the limit to 320 characters per line to make SCLP line mode console output more readable. As a result 99% of lines written during a typical boot will not be wrapped, compared to about 50% wrapped lines at 80 characters per line. Another positive side-effect of this change is that the HMC console interface is able to keep more messages in its history buffer due to fewer line-breaks being generated. In a worst case scenario this means that a 4k console buffer is emitted with the last ~400 bytes empty (320 text + 78 headers). This is more than offset by the fact that each line that is not truncated saves 78 header bytes in the buffer. As a result the actual number of emitted buffers should be about the same as with the 80 character limit. This patch also removes the differentiation between line lengths of SCLP line mode output on z/VM and non-z/VM systems. While the z/VM hypervisor adds a prefix in front of each line ('xx: ' where xx is the number of the CPU issuing the message), adjusting Linux line lengths did not significantly increase readability of console output, and makes even less of a difference with longer lines. Signed-off-by: Peter Oberparleiter <oberpar@linux.ibm.com> Tested-by: Niklas Schnelle <schnelle@linux.ibm.com> Acked-by: Heiko Carstens <hca@linux.ibm.com> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
-rw-r--r--drivers/s390/char/sclp_con.c19
-rw-r--r--drivers/s390/char/sclp_tty.c9
2 files changed, 6 insertions, 22 deletions
diff --git a/drivers/s390/char/sclp_con.c b/drivers/s390/char/sclp_con.c
index 8966a1c1b548..8c5c95bf89e0 100644
--- a/drivers/s390/char/sclp_con.c
+++ b/drivers/s390/char/sclp_con.c
@@ -41,8 +41,8 @@ static int sclp_con_suspended;
static int sclp_con_queue_running;
/* Output format for console messages */
-static unsigned short sclp_con_columns;
-static unsigned short sclp_con_width_htab;
+#define SCLP_CON_COLUMNS 320
+#define SPACES_PER_TAB 8
static void
sclp_conbuf_callback(struct sclp_buffer *buffer, int rc)
@@ -189,8 +189,8 @@ sclp_console_write(struct console *console, const char *message,
}
page = sclp_con_pages.next;
list_del((struct list_head *) page);
- sclp_conbuf = sclp_make_buffer(page, sclp_con_columns,
- sclp_con_width_htab);
+ sclp_conbuf = sclp_make_buffer(page, SCLP_CON_COLUMNS,
+ SPACES_PER_TAB);
}
/* try to write the string to the current output buffer */
written = sclp_write(sclp_conbuf, (const unsigned char *)
@@ -333,17 +333,6 @@ sclp_console_init(void)
sclp_conbuf = NULL;
timer_setup(&sclp_con_timer, sclp_console_timeout, 0);
- /* Set output format */
- if (MACHINE_IS_VM)
- /*
- * save 4 characters for the CPU number
- * written at start of each line by VM/CP
- */
- sclp_con_columns = 76;
- else
- sclp_con_columns = 80;
- sclp_con_width_htab = 8;
-
/* enable printk-access to this driver */
atomic_notifier_chain_register(&panic_notifier_list, &on_panic_nb);
register_reboot_notifier(&on_reboot_nb);
diff --git a/drivers/s390/char/sclp_tty.c b/drivers/s390/char/sclp_tty.c
index 013bcc331305..4af8084df169 100644
--- a/drivers/s390/char/sclp_tty.c
+++ b/drivers/s390/char/sclp_tty.c
@@ -54,8 +54,8 @@ static unsigned short int sclp_tty_chars_count;
struct tty_driver *sclp_tty_driver;
static int sclp_tty_tolower;
-static int sclp_tty_columns = 80;
+#define SCLP_TTY_COLUMNS 320
#define SPACES_PER_TAB 8
#define CASE_DELIMITER 0x6c /* to separate upper and lower case (% in EBCDIC) */
@@ -193,7 +193,7 @@ static int sclp_tty_write_string(const unsigned char *str, int count, int may_fa
}
page = sclp_tty_pages.next;
list_del((struct list_head *) page);
- sclp_ttybuf = sclp_make_buffer(page, sclp_tty_columns,
+ sclp_ttybuf = sclp_make_buffer(page, SCLP_TTY_COLUMNS,
SPACES_PER_TAB);
}
/* try to write the string to the current output buffer */
@@ -531,11 +531,6 @@ sclp_tty_init(void)
sclp_ttybuf = NULL;
sclp_tty_buffer_count = 0;
if (MACHINE_IS_VM) {
- /*
- * save 4 characters for the CPU number
- * written at start of each line by VM/CP
- */
- sclp_tty_columns = 76;
/* case input lines to lowercase */
sclp_tty_tolower = 1;
}