Hi,
my guess is your are not returning EOF (= 0). User space expects a
return value of 0 (EOF) to terminate reading. But your code will always
return sizeof("Hello world\n"). A fix would be to not only increment
ppos, but also check if it's already behind your data.Regards, Martin Am 30.04.19 um 13:45 schrieb [email protected]: > Greetings, > > My I2C sensor driver has a debugfs entry for development purposes. > Everything works fine with the exception of the read operation. When 'cat' > is used, the read operation is called repeatedly and indefinitely. If the > read() is changed to return 0 then, as expected, nothing is displayed. > > The pattern for the implementation is (AFAICT) right out of the book (shown > below). > > What am I missing? Any thoughts much appreciated. > > TAIA. > > RDQ > > static ssize_t sc031gs_reg_read_file(struct file *file, char __user > *user_buf, > size_t count, loff_t *ppos) > { > char *buf = 0; > ssize_t total = 0; > struct sc031gs_dev *sensor = file->private_data; > if (!sensor) > return -EINVAL; > if (*ppos < 0 || !count) > return -EINVAL; > buf = kmalloc(count, GFP_KERNEL); > if (!buf) > return -ENOMEM; > total = snprintf(buf,count,"Hello world\n"); > if (total >= 0) { > if (copy_to_user(user_buf, buf, total)) { > kfree(buf); > return -EFAULT; > } > *ppos += total; > } > kfree(buf); > return total; > } > > > _______________________________________________ > Kernelnewbies mailing list > [email protected] > https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > -- Dipl.-Inf. Martin Christian Senior Berater Entwicklung Hardware secunet Security Networks AG Tel.: +49 201 5454-3612, Fax +49 201 5454-1323 E-Mail: [email protected] Ammonstraße 74, 01067 Dresden www.secunet.com
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