Re: Getting ARM Semihosting Syslog to work on RP2040

[Jean Thomas]

Hi Lwazi and Alan,

Seems like the attachment was stripped out of my last email by the 
mailing-list. My patch looked like this:

diff --git a/nuttx/arch/arm/src/common/arm_initialize.c 
b/nuttx/arch/arm/src/common/arm_initialize.c
index c5c43507..c73c94c6 100644
--- a/nuttx/arch/arm/src/common/arm_initialize.c
+++ b/nuttx/arch/arm/src/common/arm_initialize.c
@@ -90,6 +90,10 @@ static inline void arm_color_intstack(void)
  *
  ****************************************************************************/
 
+#ifdef CONFIG_ARM_SEMIHOSTING_SYSLOG
+void setup_arm_semi_open_stdout(void);
+#endif
+
 void up_initialize(void)
 {
 #if CONFIG_ARCH_INTERRUPTSTACK > 7
@@ -135,6 +139,10 @@ void up_initialize(void)
   arm_serialinit();
 #endif
 
+#ifdef CONFIG_ARM_SEMIHOSTING_SYSLOG
+  setup_arm_semi_open_stdout();
+#endif
+
   /* Initialize the network */
 
   arm_netinitialize();
diff --git a/nuttx/arch/arm/src/common/arm_semi_syslog.c 
b/nuttx/arch/arm/src/common/arm_semi_syslog.c
index 702dbe35..17a20709 100644
--- a/nuttx/arch/arm/src/common/arm_semi_syslog.c
+++ b/nuttx/arch/arm/src/common/arm_semi_syslog.c
@@ -35,14 +35,38 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
+#define SEMI_SYSLOG_OPEN    0x01
 #define SEMI_SYSLOG_WRITEC  0x03
 #define SEMI_SYSLOG_WRITE0  0x04
+#define SEMI_SYSLOG_WRITE   0x05
 #define SEMI_SYSLOG_READC   0x07
 
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
 
+/****************************************************************************
+ * Name: arm_semi_open_stdout
+ ****************************************************************************/
+
+static int stdout_fd = -1;
+
+int arm_semi_open_stdout(void)
+{
+  int32_t params[3] = {
+    (int32_t)":tt",
+    4, // Write
+    3, // Length of ":tt"
+  };
+
+  return smh_call(SEMI_SYSLOG_OPEN, &params[0]);
+}
+
+void setup_arm_semi_open_stdout(void)
+{
+  stdout_fd = arm_semi_open_stdout();
+}
+
 /****************************************************************************
  * Name: up_putc
  ****************************************************************************/
@@ -62,10 +86,20 @@ void up_putc(int ch)
 
 void up_nputs(const char *str, size_t len)
 {
-  if (len == ~((size_t)0))
+  if (str[len - 1] == '\0')
     {
       smh_call(SEMI_SYSLOG_WRITE0, (char *)str);
     }
+  else if (len > 1 && stdout_fd != -1)
+    {
+      int32_t params[3] = {
+        stdout_fd,
+        (int32_t)str,
+        len
+      };
+
+      smh_call(SEMI_SYSLOG_WRITE, &params[0]);
+    }
   else
     {
       while (len-- > 0)

I'm using WRITE (which requires opening a file) instead of WRITE0 here because 
I wasn't receiving NULL-terminated strings from syslog buffer. 

Lwazi, did you do anything else to get it to use 0-terminated string?

Jean

> On 16 Oct 2025, at 02:24, Alan C. Assis <acas...@gmail.com> wrote:
> 
> Thank you Lwazi,
> I'll take a look after the Workshop.
> 
> BR,
> 
> Alan
> 
> On Wed, Oct 15, 2025 at 12:18 AM Lwazi Dube <lwa...@gmail.com> wrote:
> 
>> Alan,
>> I have fixed the performance issue. It is fast now. I had to make 3
>> changes.
>> 
>> 1)
>> CONFIG_SYSLOG_BUFFER=y
>> 
>> 2)
>> diff --git a/drivers/syslog/syslog_channel.c
>> b/drivers/syslog/syslog_channel.c
>> index 6bd80e6f5a..d1e47b54cf 100644
>> --- a/drivers/syslog/syslog_channel.c
>> +++ b/drivers/syslog/syslog_channel.c
>> @@ -170,6 +170,7 @@ static const struct syslog_channel_ops_s
>> g_default_channel_ops =
>>   syslog_default_putc,
>>   syslog_default_putc,
>>   NULL,
>> +  syslog_default_write,
>>   syslog_default_write
>> };
>> 
>> 3)
>> diff --git a/arch/arm/src/common/arm_semi_syslog.c
>> b/arch/arm/src/common/arm_semi_syslog.c
>> index 702dbe35da..9fecac295d 100644
>> --- a/arch/arm/src/common/arm_semi_syslog.c
>> +++ b/arch/arm/src/common/arm_semi_syslog.c
>> @@ -62,16 +62,14 @@ void up_putc(int ch)
>> 
>> void up_nputs(const char *str, size_t len)
>> {
>> -  if (len == ~((size_t)0))
>> -    {
>> +#ifdef CONFIG_SYSLOG_BUFFER
>> +      *(char *)(str + len) = 0;
>>       smh_call(SEMI_SYSLOG_WRITE0, (char *)str);
>> -    }
>> -  else
>> -    {
>> +#else
>>       while (len-- > 0)
>>         {
>>           up_putc(*str++);
>>         }
>> -    }
>> +#endif
>> }
>> #endif
>>