On Tue, Sep 27, 2011 at 4:22 AM, Graeme Russ graeme.russ@gmail.com wrote:
Hi Vadim,
On 27/09/11 08:50, Vadim Bendebury wrote:
On Wed, Aug 31, 2011 at 5:58 AM, Graeme Russ graeme.russ@gmail.com wrote:
Allow redirection of console output prior to console initialisation to a temporary buffer.
To enable this functionality, the board configuration file must define: - CONFIG_PRE_CONSOLE_BUFFER - Enable pre-console buffer - CONFIG_PRE_CON_BUF_ADDR - Base address of pre-console buffer - CONFIG_PRE_CON_BUF_SZ - Size of pre-console buffer (in bytes)
The pre-console buffer will buffer the last CONFIG_PRE_CON_BUF_SZ bytes Any earlier characters are silently dropped.
Signed-off-by: Graeme Russ graeme.russ@gmail.com
[snip]
I know I am late to the party here, but all of a sudden I need to implement something similar, albeit slightly different:
better late than never :)
- the memory could be allocated by the "cold bootprom" which starts u-boot;
Typically, the pre-console buffer would exist in the CPU cache (or similar non-(S)DRAM location)
hi Graeme,
Actually, there are many cases when u-boot starts running with memory fully initialized - ARM platforms is one case and coreboot/u-boot combination on x86 is another, but in general, yes, this buffer could be mapped to the internal CPU memory nailed to a fixed address.
- all console output needs to be saved, not just until the moment when
the console hardware is initialized.
That could be a _huge_ amount of info and highly variable. Remember, the available space for a pre-console buffer could be tiny. If this is needed, then maybe look at forking stdio instead (one branch to console, one branch to you console buffer)
Sure, if the room in the preallocated buffer is not enough, only the most recent data fitting in the space would be kept.
I don't quite understand what you mean by "forking stdio". I was thinking about introducing a separate driver for this memory stored console output, but sjg@ explained that while running from ROM u-boot supports only one console interface, so there is no way to have console stream sent to more than one driver before relocation.
I could work on top of this patch and send another one once this one has been accepted. May I suggest an improvement though:
is it really necessary to store the index in the global data structure. This requires editing all these .h files adding another unsighty conditionally compiled field. Why not to store the index as the first word in the buffer allocated for this temp storage?
I like this - but instead:
struct pre_con_buff { int idx; char *buffer[CONFIG_PRE_CON_BUF_SZ]; }
struct pre_con_buff *pre_con_buffer;
pre_con_buffer = (struct pre_con_buff *)CONFIG_PRE_CON_BUF_ADDR;
yes, this is exactly what I meant,
cheers, /vb
Regards,
Graeme