drivers/char/hvc_xen.c

   1 /*
   2  * xen console driver interface to hvc_console.c
   3  *
   4  * (c) 2007 Gerd Hoffmann <kraxel@suse.de>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
  19  */
  20
  21 #include <linux/console.h>
  22 #include <linux/delay.h>
  23 #include <linux/err.h>
  24 #include <linux/init.h>
  25 #include <linux/types.h>
  26
  27 #include <asm/xen/hypervisor.h>
  28 #include <xen/page.h>
  29 #include <xen/events.h>
  30 #include <xen/interface/io/console.h>
  31 #include <xen/hvc-console.h>
  32
  33 #include "hvc_console.h"
  34
  35 #define HVC_COOKIE   0x58656e /* "Xen" in hex */
  36
  37 static struct hvc_struct *hvc;
  38 static int xencons_irq;
  39
  40 /* ------------------------------------------------------------------ */
  41
  42 static inline struct xencons_interface *xencons_interface(void)
  43 {
  44         return mfn_to_virt(xen_start_info->console.domU.mfn);
  45 }
  46
  47 static inline void notify_daemon(void)
  48 {
  49         /* Use evtchn: this is called early, before irq is set up. */
  50         notify_remote_via_evtchn(xen_start_info->console.domU.evtchn);
  51 }
  52
  53 static int write_console(uint32_t vtermno, const char *data, int len)
  54 {
  55         struct xencons_interface *intf = xencons_interface();
  56         XENCONS_RING_IDX cons, prod;
  57         int sent = 0;
  58
  59         cons = intf->out_cons;
  60         prod = intf->out_prod;
  61         mb();                   /* update queue values before going on */
  62         BUG_ON((prod - cons) > sizeof(intf->out));
  63
  64         while ((sent < len) && ((prod - cons) < sizeof(intf->out)))
  65                 intf->out[MASK_XENCONS_IDX(prod++, intf->out)] = data[sent++];
  66
  67         wmb();                  /* write ring before updating pointer */
  68         intf->out_prod = prod;
  69
  70         notify_daemon();
  71         return sent;
  72 }
  73
  74 static int read_console(uint32_t vtermno, char *buf, int len)
  75 {
  76         struct xencons_interface *intf = xencons_interface();
  77         XENCONS_RING_IDX cons, prod;
  78         int recv = 0;
  79
  80         cons = intf->in_cons;
  81         prod = intf->in_prod;
  82         mb();                   /* get pointers before reading ring */
  83         BUG_ON((prod - cons) > sizeof(intf->in));
  84
  85         while (cons != prod && recv < len)
  86                 buf[recv++] = intf->in[MASK_XENCONS_IDX(cons++, intf->in)];
  87
  88         mb();                   /* read ring before consuming */
  89         intf->in_cons = cons;
  90
  91         notify_daemon();
  92         return recv;
  93 }
  94
  95 static struct hv_ops hvc_ops = {
  96         .get_chars = read_console,
  97         .put_chars = write_console,
  98 };
  99
 100 static int __init xen_init(void)
 101 {
 102         struct hvc_struct *hp;
 103
 104         if (!is_running_on_xen())
 105                 return 0;
 106
 107         xencons_irq = bind_evtchn_to_irq(xen_start_info->console.domU.evtchn);
 108         if (xencons_irq < 0)
 109                 xencons_irq = 0 /* NO_IRQ */;
 110         hp = hvc_alloc(HVC_COOKIE, xencons_irq, &hvc_ops, 256);
 111         if (IS_ERR(hp))
 112                 return PTR_ERR(hp);
 113
 114         hvc = hp;
 115         return 0;
 116 }
 117
 118 static void __exit xen_fini(void)
 119 {
 120         if (hvc)
 121                 hvc_remove(hvc);
 122 }
 123
 124 static int xen_cons_init(void)
 125 {
 126         if (!is_running_on_xen())
 127                 return 0;
 128
 129         hvc_instantiate(HVC_COOKIE, 0, &hvc_ops);
 130         return 0;
 131 }
 132
 133 module_init(xen_init);
 134 module_exit(xen_fini);
 135 console_initcall(xen_cons_init);
 136
 137 static void xenboot_write_console(struct console *console, const char *string,
 138                                   unsigned len)
 139 {
 140         unsigned int linelen, off = 0;
 141         const char *pos;
 142
 143         while (off < len && NULL != (pos = strchr(string+off, '\n'))) {
 144                 linelen = pos-string+off;
 145                 if (off + linelen > len)
 146                         break;
 147                 write_console(0, string+off, linelen);
 148                 write_console(0, "\r\n", 2);
 149                 off += linelen + 1;
 150         }
 151         if (off < len)
 152                 write_console(0, string+off, len-off);
 153 }
 154
 155 struct console xenboot_console = {
 156         .name           = "xenboot",
 157         .write          = xenboot_write_console,
 158         .flags          = CON_PRINTBUFFER | CON_BOOT,
 159 };