Come usare
- Copia il comando e controlla il pacchetto prima di installarlo nel tuo ambiente agente.
- Controlla strumenti, credenziali e ambienti richiesti nel documento originale.
- Descrivi input e risultato desiderato; confronta l’output con le fonti.
npx skills add https://github.com/mohitmishra786/low-level-dev-skills --skill bus-drivers-i2c-spiPrima di iniziare
- L’installazione non include abbonamenti, quote API o accesso ai file.
- Stelle e installazioni indicano attività, non un test indipendente di qualità o sicurezza.
Documento Skill originale
Contenuto dal repository con titoli, esempi, codice, tabelle, link e immagini preservati.
Bus Drivers (I2C and SPI)
Purpose
Guide agents through Linux I2C and SPI client drivers: bus registration, i2c_transfer / spi_sync, regmap abstraction, DT compatible on bus children, and probe patterns — complementing platform MMIO drivers in skills/kernel/device-drivers.
When to Use
- Sensor or PMIC on I2C/SPI bus
- Converting bare-metal SPI register reads to kernel driver
- Using
regmapfor multi-byte register access - Debugging
-EREMOTEIOor missing ACK
Workflow
1. I2C client driver
c
#include <linux/i2c.h>
#include <linux/mod_devicetable.h>
static int my_probe(struct i2c_client *client)
{
struct regmap *map;
map = devm_regmap_init_i2c(client, &my_regmap_config);
if (IS_ERR(map))
return PTR_ERR(map);
dev_info(&client->dev, "probed at 0x%02x\n", client->addr);
return 0;
}
static const struct of_device_id my_of_id[] = {
{ .compatible = "vendor,sensor" },
{ }
};
MODULE_DEVICE_TABLE(of, my_of_id);
static const struct i2c_device_id my_id[] = {
{ "mysensor", 0 },
{ }
};
MODULE_DEVICE_TABLE(i2c, my_id);
static struct i2c_driver my_driver = {
.probe = my_probe,
.remove = my_remove,
.driver = { .name = "mysensor", .of_match_table = my_of_id },
.id_table = my_id,
};
module_i2c_driver(my_driver);DT child:
dts
i2c1 {
sensor@48 {
compatible = "vendor,sensor";
reg = <0x48>;
};
};2. Raw I2C transfer
c
u8 reg = 0x0F, val;
struct i2c_msg msgs[] = {
{ .addr = client->addr, .flags = 0, .len = 1, .buf = ® },
{ .addr = client->addr, .flags = I2C_M_RD, .len = 1, .buf = &val },
};
ret = i2c_transfer(client->adapter, msgs, 2);3. SPI driver
c
static int spi_probe(struct spi_device *spi)
{
spi->mode = SPI_MODE_0;
spi->bits_per_word = 8;
spi_setup(spi);
struct spi_transfer t = {
.tx_buf = tx,
.rx_buf = rx,
.len = len,
};
struct spi_message m;
spi_message_init(&m);
spi_message_add_tail(&t, &m);
return spi_sync(spi, &m);
}
static struct spi_driver spi_drv = {
.probe = spi_probe,
.driver = { .name = "my-spi", .of_match_table = my_of_match },
};
module_spi_driver(spi_drv);4. regmap (preferred for register maps)
c
static const struct regmap_config my_regmap_config = {
.reg_bits = 8,
.val_bits = 8,
.max_register = 0x7F,
};
regmap_read(map, REG_STATUS, &val);
regmap_write(map, REG_CTRL, CTRL_ENABLE);
regmap_update_bits(map, REG_CTRL, MASK, ENABLE);5. Debug
bash
i2cdetect -y 1
i2cdump -y 1 0x48
cat /sys/bus/i2c/devices/i2c-1/1-0048/name6. Agent usage
/bus-drivers-i2c-spi Write regmap-based driver for I2C PMIC at 0x58Common Problems
| Symptom | Cause | Fix |
|---|---|---|
-EREMOTEIO | NACK — wrong address | i2cdetect; check reg in DT |
| SPI mode wrong | CPOL/CPHA mismatch | Match datasheet + spi->mode |
| Probe defer | Regulator/clock supplier | Return -EPROBE_DEFER |
| regmap -EIO | 16-bit vs 8-bit reg | Set reg_bits, val_bits |
| DMA not used | Small spi_sync OK | spi_sync_transfer for bulk |
Related Skills
skills/kernel/device-drivers— IRQ, DMA, PM runtimeskills/kernel-dev/device-tree— bus child nodesskills/baremetal/spi-i2c-baremetal— register-level protocolskills/kernel-dev/platform-device-model— driver model parallelsskills/kernel-dev/writing-char-drivers— expose sensor via char dev
