Re: [PATCH v3 4/4] mmc: core: Add MMC pstore backend driver

From: Kamal Dasu

Date: Fri Apr 10 2026 - 11:58:21 EST

On Fri, Mar 20, 2026 at 11:18 AM kernel test robot <lkp@xxxxxxxxx> wrote:

Hi Kamal,

kernel test robot noticed the following build warnings:

[auto build test WARNING on linus/master]
[also build test WARNING on v7.0-rc4 next-20260319]
[cannot apply to ulf-hansson-mmc-mirror/next]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url: https://github.com/intel-lab-lkp/linux/commits/Kamal-Dasu/mmc-core-Add-panic-context-host-operations-for-pstore-backends/20260320-064639
base: linus/master
patch link: https://lore.kernel.org/r/20260319185705.1516950-5-kamal.dasu%40broadcom.com
patch subject: [PATCH v3 4/4] mmc: core: Add MMC pstore backend driver
config: m68k-allyesconfig (https://download.01.org/0day-ci/archive/20260320/202603202338.OYFgRuuU-lkp@xxxxxxxxx/config)
compiler: m68k-linux-gcc (GCC) 15.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260320/202603202338.OYFgRuuU-lkp@xxxxxxxxx/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Closes: https://lore.kernel.org/oe-kbuild-all/202603202338.OYFgRuuU-lkp@xxxxxxxxx/

All warnings (new ones prefixed by >>):

drivers/mmc/core/mmcpstore.c: In function 'mmcpstore_register_for_card':
>> drivers/mmc/core/mmcpstore.c:1016:23: warning: variable 'offset_bytes' set but not used [-Wunused-but-set-variable]
1016 | unsigned long offset_bytes;
| ^~~~~~~~~~~~
--
>> Warning: drivers/mmc/core/mmcpstore.c:250 function parameter 'sect_offset' not described in 'mmcpstore_do_request_internal'
>> Warning: drivers/mmc/core/mmcpstore.c:573 expecting prototype for mmcpstore_read(). Prototype was for mmcpstore_read_zone() instead
>> Warning: drivers/mmc/core/mmcpstore.c:1248 function parameter 'disk' not described in 'mmcpstore_card_add'
>> Warning: drivers/mmc/core/mmcpstore.c:250 function parameter 'sect_offset' not described in 'mmcpstore_do_request_internal'
>> Warning: drivers/mmc/core/mmcpstore.c:1248 function parameter 'disk' not described in 'mmcpstore_card_add'

Fixed all warnings and sent a v4 version a couple of weeks back. Please review the v4 changes.

vim +/offset_bytes +1016 drivers/mmc/core/mmcpstore.c

998
999 /**
1000 * mmcpstore_register_for_card - Register pstore for specific MMC card
1001 * @card: MMC card to register pstore for
1002 * @dev_name_param: Device path (e.g., "/dev/mmcblk1p5")
1003 * @disk: gendisk for the card (non-NULL for builtin path, NULL for module)
1004 *
1005 * Returns: 0 on success, negative error on failure
1006 */
1007 static int mmcpstore_register_for_card(struct mmc_card *card,
1008 const char *dev_name_param,
1009 struct gendisk *disk)
1010 {
1011 struct mmcpstore_context *cxt;
1012 struct pstore_blk_config conf;
1013 struct file *bdev_file;
1014 struct block_device *bdev;
1015 sector_t partition_sectors;
> 1016 unsigned long offset_bytes;
1017 unsigned long required_size;
1018 unsigned long kmsg_records;
1019 int ret;
1020
1021 /*
1022 * Open the block device to get partition start sector and size.
1023 * When called from mmc_blk_probe() (builtin path), /dev/ may not
1024 * be mounted yet, so use the gendisk + partition number to look
1025 * up the dev_t directly.
1026 */
1027 if (disk) {
1028 int partno = mmcpstore_extract_partno(dev_name_param);
1029 dev_t devt;
1030
1031 if (partno < 0) {
1032 pr_warn("Cannot parse partition from %s\n",
1033 dev_name_param);
1034 return -EINVAL;
1035 }
1036 devt = part_devt(disk, partno);
1037 if (!devt) {
1038 pr_warn("Partition %d not found on %s\n",
1039 partno, disk->disk_name);
1040 return -ENODEV;
1041 }
1042 bdev_file = bdev_file_open_by_dev(devt, BLK_OPEN_READ,
1043 NULL, NULL);
1044 } else {
1045 bdev_file = bdev_file_open_by_path(dev_name_param,
1046 BLK_OPEN_READ, NULL, NULL);
1047 }
1048 if (IS_ERR(bdev_file)) {
1049 ret = PTR_ERR(bdev_file);
1050 pr_warn("Failed to open device %s: %d\n", dev_name_param, ret);
1051 return ret;
1052 }
1053 bdev = file_bdev(bdev_file);
1054
1055 cxt = mmcpstore_ctx;
1056 if (!cxt) {
1057 pr_err("No context available\n");
1058 fput(bdev_file);
1059 return -ENODEV;
1060 }
1061
1062 /* pre-allocated buffer for alignment handling */
1063 cxt->buffer_size = MMC_PSTORE_MAX_BUFFER_SIZE;
1064 cxt->buffer = kmalloc(cxt->buffer_size, GFP_KERNEL);
1065 if (!cxt->buffer) {
1066 pr_err("Failed to allocate %zu bytes for pstore buffer\n",
1067 cxt->buffer_size);
1068 fput(bdev_file);
1069 return -ENOMEM;
1070 }
1071
1072 if (!(card->host->caps & MMC_CAP_NONREMOVABLE)) {
1073 dev_err(&card->dev, "MMC pstore only supports non-removable cards (eMMC)\n");
1074 dev_err(&card->dev, "This card is removable and not suitable for pstore\n");
1075 ret = -EOPNOTSUPP;
1076 goto err_free;
1077 }
1078
1079 /* Initialize context */
1080 cxt->card = card;
1081 strscpy(cxt->card_name, dev_name_param, sizeof(cxt->card_name));
1082 cxt->start_sect = bdev->bd_start_sect;
1083 cxt->size = bdev_nr_bytes(bdev);
1084
1085 /* Apply user-specified sector offset and count within the partition */
1086 if (part_sect_ofs > 0 || part_sect_cnt > 0) {
1087 if ((part_sect_ofs > 0 && part_sect_cnt == 0) ||
1088 (part_sect_ofs == 0 && part_sect_cnt > 0)) {
1089 dev_err(&card->dev, "sector_offset and sector_count must be specified\n");
1090 ret = -EINVAL;
1091 goto err_free;
1092 }
1093
1094 /* Validate offset and count */
1095 partition_sectors = cxt->size >> 9;
1096 offset_bytes = part_sect_ofs * MMC_PSTORE_SECTOR_SIZE;
1097
1098 if (part_sect_ofs >= partition_sectors) {
1099 dev_err(&card->dev, "Sector offset %lu >= partition size %llu sectors\n",
1100 part_sect_ofs, partition_sectors);
1101 ret = -EINVAL;
1102 goto err_free;
1103 }
1104
1105 if (part_sect_ofs + part_sect_cnt > partition_sectors) {
1106 dev_err(&card->dev, "Sector range %lu-%lu exceeds partition size %llu sectors\n",
1107 part_sect_ofs,
1108 part_sect_ofs + part_sect_cnt - 1,
1109 partition_sectors);
1110 ret = -EINVAL;
1111 goto err_free;
1112 }
1113
1114 cxt->start_sect += part_sect_ofs;
1115 cxt->size = part_sect_cnt * MMC_PSTORE_SECTOR_SIZE;
1116
1117 pr_info("Pstore will use: sectors %lu-%lu (%llu bytes total)\n",
1118 part_sect_ofs, part_sect_ofs + part_sect_cnt - 1,
1119 cxt->size);
1120 }
1121
1122 fput(bdev_file);
1123
1124 /* Configure pstore */
1125 memset(&conf, 0, sizeof(conf));
1126 strscpy(conf.device, dev_name_param, sizeof(conf.device));
1127 conf.max_reason = KMSG_DUMP_PANIC;
1128
1129 /* Fetch pstore configuration including sizes from module parameters */
1130 ret = pstore_blk_get_config(&conf);
1131 if (ret != 0) {
1132 pr_err("Failed to get pstore block config: %d\n", ret);
1133 goto err_free;
1134 }
1135
1136 /* Validate size requirements */
1137 ret = mmcpstore_calculate_sizes(cxt, &conf, &required_size,
1138 &kmsg_records);
1139 if (ret)
1140 goto err_free;
1141
1142 pr_debug("Pstore requirements: kmsg=%lu KB, pmsg=%lu KB, console=%lu KB, ftrace=%lu KB\n",
1143 MMC_PSTORE_BYTES_TO_KB(conf.kmsg_size),
1144 MMC_PSTORE_BYTES_TO_KB(conf.pmsg_size),
1145 MMC_PSTORE_BYTES_TO_KB(conf.console_size),
1146 MMC_PSTORE_BYTES_TO_KB(conf.ftrace_size));
1147 pr_debug("Pstore capacity: ~%lu kmsg records possible (%lu KB each, varies with compression)\n",
1148 kmsg_records, MMC_PSTORE_BYTES_TO_KB(conf.kmsg_size));
1149
1150 /* Set up pstore device info */
1151 cxt->dev.flags = 0; /* Support all backends */
1152 if (conf.kmsg_size > 0)
1153 cxt->dev.flags |= PSTORE_FLAGS_DMESG;
1154 if (conf.pmsg_size > 0)
1155 cxt->dev.flags |= PSTORE_FLAGS_PMSG;
1156 if (conf.console_size > 0)
1157 cxt->dev.flags |= PSTORE_FLAGS_CONSOLE;
1158 if (conf.ftrace_size > 0)
1159 cxt->dev.flags |= PSTORE_FLAGS_FTRACE;
1160
1161 /* Set up zone structure for pstore/zone API */
1162 cxt->dev.zone.read = mmcpstore_read_zone;
1163 cxt->dev.zone.write = mmcpstore_write;
1164 cxt->dev.zone.panic_write = mmcpstore_panic_write;
1165 cxt->dev.zone.total_size = cxt->size;
1166 cxt->dev.zone.kmsg_size = conf.kmsg_size;
1167 cxt->dev.zone.pmsg_size = conf.pmsg_size;
1168 cxt->dev.zone.console_size = conf.console_size;
1169 cxt->dev.zone.ftrace_size = conf.ftrace_size;
1170 cxt->dev.zone.max_reason = conf.max_reason;
1171 cxt->dev.zone.name = "mmcpstore";
1172 cxt->dev.zone.owner = THIS_MODULE;
1173
1174 mutex_init(&cxt->lock);
1175
1176 /*
1177 * Set state to READY before registration because register_pstore_device()
1178 * triggers pstore_zone recovery which calls our read callback, and the
1179 * read callback requires state == READY to proceed.
1180 */
1181 mutex_lock(&mmcpstore_global_lock);
1182 cxt->state = MMCPSTORE_STATE_READY;
1183 mutex_unlock(&mmcpstore_global_lock);
1184
1185 ret = register_pstore_device(&cxt->dev);
1186 if (ret) {
1187 dev_err(&card->dev, "Failed to register pstore device: %d\n",
1188 ret);
1189 mutex_lock(&mmcpstore_global_lock);
1190 cxt->state = MMCPSTORE_STATE_UNINITIALIZED;
1191 mutex_unlock(&mmcpstore_global_lock);
1192 goto err_free;
1193 }
1194
1195 dev_info(&card->dev, "MMC pstore backend registered successfully\n");
1196 dev_info(&card->dev, "Device: %s, Size: %llu bytes (%llu KB)\n",
1197 dev_name_param, cxt->size, MMC_PSTORE_BYTES_TO_KB(cxt->size));
1198 dev_info(&card->dev, "Start sector: %llu, Sector count: %llu\n",
1199 cxt->start_sect, cxt->size / MMC_PSTORE_SECTOR_SIZE);
1200 dev_info(&card->dev, "Pstore components: kmsg=%lu KB, pmsg=%lu KB, console=%lu KB, ftrace=%lu KB\n",
1201 MMC_PSTORE_BYTES_TO_KB(conf.kmsg_size),
1202 MMC_PSTORE_BYTES_TO_KB(conf.pmsg_size),
1203 MMC_PSTORE_BYTES_TO_KB(conf.console_size),
1204 MMC_PSTORE_BYTES_TO_KB(conf.ftrace_size));
1205
1206 return 0;
1207
1208 err_free:
1209 kfree(cxt->buffer);
1210 /* Don't free cxt here - it's the global context */
1211 return ret;
1212 }
1213

Thanks

Kamal

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0-DAY CI Kernel Test Service
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