esp_vfs_fat_register and httpd not working together without USE_ONLY_LWIP_SELECT

[felixcollins]

I have been having a problem where the httpd will not work after calling esp_vfs_fat_sdmmc_mount(). It seems the problem is fixed by running menuconfig and choosing the "lwip select only" option. Component config / LWIP /USE_ONLY_LWIP_SELECT [=y].

It seems the problem is that the select() call in the httpd returns data on the wrong file descriptor after esp_vfs_fat_sdmmc_mount() is called.

I assume this is a bug? If not then it should be documented that the USE_ONLY_LWIP_SELECT is required.

[ESP_Roland]

Hi felixcollins.

Thank you for reporting this issue. It is probably a bug based on your description. However, I cannot reproduce it. The result for select() is fine on my end after calling esp_vfs_fat_sdmmc_mount(). Would it be possible to give us a minimal (not)working example and report the issue at https://github.com/espressif/esp-idf/issues?

[felixcollins]

Done... https://github.com/espressif/esp-idf/issues/3554