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Re: [Xen-devel] [PATCH v4 3/7] xen: introduce a generic framebuffer driver
On 09/01/13 14:05, Stefano Stabellini wrote:
On Wed, 9 Jan 2013, Jan Beulich wrote:
On 08.01.13 at 21:03, Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
wrote:
--- /dev/null
+++ b/xen/drivers/video/lfb.c
@@ -0,0 +1,206 @@
+/******************************************************************************
+ * lfb.c
+ *
+ * linear frame buffer handling.
+ */
+
+#include <xen/config.h>
+#include <xen/kernel.h>
+#include <xen/lib.h>
+#include <xen/errno.h>
+#include "lfb.h"
+#include "font.h"
+
+#define MAX_XRES 1900
+#define MAX_YRES 1200
+#define MAX_BPP 4
+#define MAX_FONT_W 8
+#define MAX_FONT_H 16
+static __initdata unsigned int line_len[MAX_XRES / MAX_FONT_W];
+static __initdata unsigned char lbuf[MAX_XRES * MAX_BPP];
+static __initdata unsigned char text_buf[(MAX_XRES / MAX_FONT_W) * \
+ (MAX_YRES / MAX_FONT_H)];
Imo it would be better to move all these __initdata definitions
do to where the using __init functions actually live, to make
sure unintended use of them in non-__init ones is noticed.
OK
+
+struct lfb_status {
+ struct lfb_prop lfbp;
+
+ unsigned char *lbuf, *text_buf;
+ unsigned int *line_len;
+ unsigned int xpos, ypos;
+};
+static struct lfb_status lfb;
+
+static void lfb_show_line(
+ const unsigned char *text_line,
+ unsigned char *video_line,
+ unsigned int nr_chars,
+ unsigned int nr_cells)
+{
+ unsigned int i, j, b, bpp, pixel;
+
+ bpp = (lfb.lfbp.bits_per_pixel + 7) >> 3;
+
+ for ( i = 0; i < lfb.lfbp.font->height; i++ )
+ {
+ unsigned char *ptr = lfb.lbuf;
+
+ for ( j = 0; j < nr_chars; j++ )
+ {
+ const unsigned char *bits = lfb.lfbp.font->data;
+ bits += ((text_line[j] * lfb.lfbp.font->height + i) *
+ ((lfb.lfbp.font->width + 7) >> 3));
+ for ( b = lfb.lfbp.font->width; b--; )
+ {
+ pixel = (*bits & (1u<<b)) ? lfb.lfbp.pixel_on : 0;
+ memcpy(ptr, &pixel, bpp);
+ ptr += bpp;
+ }
+ }
+
+ memset(ptr, 0, (lfb.lfbp.width - nr_chars * lfb.lfbp.font->width) *
bpp);
+ memcpy(video_line, lfb.lbuf, nr_cells * lfb.lfbp.font->width * bpp);
+ video_line += lfb.lfbp.bytes_per_line;
+ }
+}
+
+/* Fast mode which redraws all modified parts of a 2D text buffer. */
+void lfb_redraw_puts(const char *s)
+{
+ unsigned int i, min_redraw_y = lfb.ypos;
+ char c;
+
+ /* Paste characters into text buffer. */
+ while ( (c = *s++) != '\0' )
+ {
+ if ( (c == '\n') || (lfb.xpos >= lfb.lfbp.text_columns) )
+ {
+ if ( ++lfb.ypos >= lfb.lfbp.text_rows )
+ {
+ min_redraw_y = 0;
+ lfb.ypos = lfb.lfbp.text_rows - 1;
+ memmove(lfb.text_buf, lfb.text_buf + lfb.lfbp.text_columns,
+ lfb.ypos * lfb.lfbp.text_columns);
+ memset(lfb.text_buf + lfb.ypos * lfb.lfbp.text_columns, 0,
lfb.xpos);
+ }
+ lfb.xpos = 0;
+ }
+
+ if ( c != '\n' )
+ lfb.text_buf[lfb.xpos++ + lfb.ypos * lfb.lfbp.text_columns] = c;
+ }
+
+ /* Render modified section of text buffer to VESA linear framebuffer. */
+ for ( i = min_redraw_y; i <= lfb.ypos; i++ )
+ {
+ const unsigned char *line = lfb.text_buf + i * lfb.lfbp.text_columns;
+ unsigned int width;
+
+ for ( width = lfb.lfbp.text_columns; width; --width )
+ if ( line[width - 1] )
+ break;
+ lfb_show_line(line,
+ lfb.lfbp.lfb + i * lfb.lfbp.font->height *
lfb.lfbp.bytes_per_line,
+ width, max(lfb.line_len[i], width));
+ lfb.line_len[i] = width;
+ }
+
+ lfb.lfbp.flush();
+}
+
+/* Slower line-based scroll mode which interacts better with dom0. */
+void lfb_scroll_puts(const char *s)
+{
+ unsigned int i;
+ char c;
+
+ while ( (c = *s++) != '\0' )
+ {
+ if ( (c == '\n') || (lfb.xpos >= lfb.lfbp.text_columns) )
+ {
+ unsigned int bytes = (lfb.lfbp.width *
+ ((lfb.lfbp.bits_per_pixel + 7) >> 3));
+ unsigned char *src = lfb.lfbp.lfb + lfb.lfbp.font->height *
lfb.lfbp.bytes_per_line;
+ unsigned char *dst = lfb.lfbp.lfb;
+
+ /* New line: scroll all previous rows up one line. */
+ for ( i = lfb.lfbp.font->height; i < lfb.lfbp.height; i++ )
+ {
+ memcpy(dst, src, bytes);
+ src += lfb.lfbp.bytes_per_line;
+ dst += lfb.lfbp.bytes_per_line;
+ }
+
+ /* Render new line. */
+ lfb_show_line(
+ lfb.text_buf,
+ lfb.lfbp.lfb + (lfb.lfbp.text_rows-1) * lfb.lfbp.font->height
* lfb.lfbp.bytes_per_line,
Long line?
Right
The calculation of
lfb.lfbp.lfb + lfb.lfbp.font->height * lfb.lfbp.bytes_per_line;
is done twice in the above section - surely that's constant over time, so could be stored
in another local variable - thus making the line shorter and at the same time more
obvious that "it's the same thing".
--
Mats
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