libexplain  1.4.D001
libexplain/buffer/v4l2_frequency.c
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00001 /*
00002  * libexplain - a library of system-call-specific strerror replacements
00003  * Copyright (C) 2011, 2013 Peter Miller
00004  *
00005  * This program is free software; you can redistribute it and/or modify
00006  * it under the terms of the GNU Lesser General Public License as
00007  * published by the Free Software Foundation; either version 3 of the
00008  * License, or (at your option) any later version.
00009  *
00010  * This program is distributed in the hope that it will be useful,
00011  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00012  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00013  * Lesser General Public License for more details.
00014  *
00015  * You should have received a copy of the GNU Lesser General Public License
00016  * along with this program. If not, see <http://www.gnu.org/licenses/>.
00017  */
00018 
00019 #include <libexplain/ac/errno.h>
00020 #include <libexplain/ac/linux/videodev2.h>
00021 #include <libexplain/ac/string.h>
00022 #include <libexplain/ac/sys/ioctl.h>
00023 
00024 #include <libexplain/buffer/int32_t.h>
00025 #include <libexplain/buffer/pointer.h>
00026 #include <libexplain/buffer/v4l2_frequency.h>
00027 #include <libexplain/buffer/v4l2_tuner_type.h>
00028 #include <libexplain/is_efault.h>
00029 #include <libexplain/sizeof.h>
00030 
00031 
00032 #ifdef HAVE_LINUX_VIDEODEV2_H
00033 
00034 void
00035 explain_buffer_v4l2_frequency(explain_string_buffer_t *sb,
00036     const struct v4l2_frequency *data, int extra)
00037 {
00038     if (explain_is_efault_pointer(data, sizeof(*data)))
00039     {
00040         explain_buffer_pointer(sb, data);
00041         return;
00042     }
00043 
00044     explain_string_buffer_puts(sb, "{ tuner = ");
00045     explain_buffer_uint32_t(sb, data->tuner);
00046     if (extra)
00047     {
00048         explain_string_buffer_puts(sb, ", type = ");
00049         explain_buffer_v4l2_tuner_type(sb, data->type);
00050         explain_string_buffer_puts(sb, ", frequency = ");
00051         explain_buffer_uint32_t(sb, data->frequency);
00052         if (!explain_uint32_array_all_zero(data->reserved,
00053             SIZEOF(data->reserved)))
00054         {
00055             explain_string_buffer_puts(sb, ", reserved = ");
00056             explain_buffer_uint32_array(sb, data->reserved,
00057                 SIZEOF(data->reserved));
00058         }
00059     }
00060     explain_string_buffer_puts(sb, " }");
00061 }
00062 
00063 
00064 int
00065 explain_v4l2_frequency_get_n(int fildes)
00066 {
00067     const int       max = 200;
00068     int             lo;
00069     int             hi;
00070 
00071     lo = 0;
00072     hi = max;
00073     for (;;)
00074     {
00075         struct v4l2_frequency qry;
00076         int             mid;
00077 
00078         mid = (lo + hi) / 2;
00079         memset(&qry, 0, sizeof(qry));
00080         qry.tuner = mid;
00081         if (ioctl(fildes, VIDIOC_G_FREQUENCY, &qry) >= 0)
00082         {
00083             if (hi <= 0 && lo <= 0)
00084                 return -1;
00085             /* mid < n */
00086             lo = mid + 1;
00087             if (lo > hi)
00088             {
00089                 done:
00090                 if (lo >= max)
00091                 {
00092                     /*
00093                      * Many drivers have the same bug: they do not check
00094                      * data->tuner at all, with the result that they appear
00095                      * to support an infinite number of frequencies.
00096                      */
00097                     return 1;
00098                 }
00099                 return lo;
00100             }
00101         }
00102         else if (errno != EINVAL)
00103         {
00104             return -1;
00105         }
00106         else
00107         {
00108             if (hi <= 0 && lo <= 0)
00109                 return -1;
00110             /* mid >= n */
00111             hi = mid - 1;
00112             if (lo >= hi)
00113                 goto done;
00114         }
00115     }
00116 }
00117 
00118 #endif
00119 
00120 /* vim: set ts=8 sw=4 et : */